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FAQs about Sea Urchins, Sand Dollar Compatibility

Related Articles: Sea Urchins,

Related FAQs: Urchins 1, Urchins 2, Urchins 3, Urchin Identification, Urchin Behavior, Urchin Selection, Urchin System, Urchin Feeding, Urchin Disease, Urchin Reproduction,

Not with: Large wrasses, puffers, triggers... all eat urchins in the wild...
With Harlequin Shrimp? Lunch

Long Spine Urchin with Zebra Moral Eel, comp.      9/21/19
Hi Bob -
Would a large long spine urchin with the body size of around a tennis ball be left alone by a Zebra Moral Eel that's about 2 feet in length? I've read Zebra Moral Eels feed on urchins, but I thought maybe the long spine urchin might be an exception.
<Mmm; I don't think it's a good idea to place morays in systems with sharp objects period... their vision's not all that good, and they have a habit of bumping into most all>
Further, I suspect a Zebra Moral Eel would eat a chocolate chip starfish?
<I don't think so, no. They mainly eat crustaceans in the wild>
BTW, I wanted to report back that your knowledge and feedback was correct on a question I asked last week. I've witnessed a large pin cushion urchin (close to 4 inches in diameter) has eaten cyanobacteria (red) off my live rock as you suspected might occur.
Thank you, John
<Cheers John. BobF>

Re: Long Spine Urchin with Zebra Moral Eel; plus BGA eater      9/22/19
Bob -
Thank you very much you're most helpful as always! Your feedback definitely helps me properly plan some aquatic living arrangements.
<Am so glad to share, aid your efforts... promote the proper/appropriate use of resources John>
Here's a photo of the pin cushion urchin I previously referenced with a smaller long spine that shows some cyanobacteria (red) removed from the rocks (see rock closest to the gravel).
Thanks, John
<Thank you for sharing. Bob Fenner>

Urchin compatibility   2/1/18
Hi, I was wonder which, if any, sea urchins are compatible with a common starfish in a 75 gallon tank? Thank you :)
<Most all are; though I hasten to mention that some urchin species choices are better than others. See WWM re the Echinoids. Bob Fenner>

CC Starfish; incomp. w/ Urchin/s      10/1/15
Hi, I came home today to find my chocolate chip starfish laying on the bottom of the tank with my sea urchin on top of him.
<Yikes... Some Urchins eat Seastars...>
I had a suspicion something wasn't right so I moved the sea urchin to find he had eatin one leg off the star fish. Although the star fish looked normal I immediately assumed he was dead.. he seemed stiff as well. I moved him, and began to see movement. So I then picked him up and held him against the glass. He latched on and has been moving around for an hour or so. My question is will he survive and will the leg grow back?
<IF this CC survives, conditions are propitious, it may regenerate. I'd be keeping the two separated. IF you have a refugium, I'd move the star there>
Also what would cause the urchin to do this?
<Hunger, predation... opportunity>
They have been in the tank together for about 6 months. And the starfish does not appear sick in anyway. Thank you!
<Welcome. Bob Fenner>

Longspine Urchin (not particularly reef safe) – 06/01/13
Dear Crew,
<<Hiya Bryce>>
This is going to be a relatively simple email, but I need this problem solved.
I have a tank with a Galaxea Coral, Candycane Coral, Birdsnest Coral, and Longspine Urchin. The urchin has left every coral alone except the Candycane, which it is fond of eating.
<<In my experience, these animals will consume most any coral at times>>
I was under the impression that it was herbivorous.
<<Mmm, no…at least not in the confines of an aquarium…can be quite opportunistic>>
Could it be that the urchin is starving?
And, if it is starving, why is it only eating the Candycane?
<<Perhaps the least noxious of the lot>>
I have attempted to feed it Nori before, but it rejected the Nori.
<<These critters will eat whatever “suits” them…and are best left to very large aquaria where their opportunistic nature may do less harm…in my humble opinion>>
Have a terrific day.
<<And to you in kind…EricR>>

Stung by Long-Spine Urchin  /RMF     4/25/13
Today I was moving an Acro frag up a bit higher in my tank, around the same time a crab moved and knocked it over. Without thinking I reached for the frag, and my index finger met my Long-Spine Urchin. I do not think that the spine broke under the skin, and I dissected my finger with tweezers in the process. It also hurt like nothing else I have felt before, and there was initially lots of inflammation. I ran my finger under hot water because I had no other clue what to do (also remembered this is how to treat Lionfish stings), but am I correct in thinking that a secondary infection from the exposure is of much more concern?
<Not likely problematical, but I would run the wound site under hot water for a few minutes, apply some antibiotic cream... And not worry. BobF>
Stung by Long Spine Urchin    /James   4/25/2013

Today I was moving an Acro frag up a bit higher in my tank, around the  same time a crab moved and knocked it over. Without thinking I reached for the frag, and my index finger met my Long-Spine Urchin. I do not think that the spine broke under the skin, and I dissected my finger with tweezers in the process. It also hurt like nothing else I have felt before, and there was initially lots of inflammation.
I ran my finger under hot water because I had no other clue what to do (also remembered this is how to treat Lionfish stings), but am I correct in thinking that a secondary infection from the exposure is of much more concern?
<Do read here Bryce. 
James (Salty Dog)>

Quick Question, Sharks, Urchins as tankmates     12/17/12
First off, thank you so much for the great info, I've been cruising the site for over straight six hours now!
<Ahh! About this long for me with the slow connection here in Cozumel>
After many months of research and planning I recently decided to down size my 180 mixed reef and use the existing setup and some rock to house a single Coral Catshark (*Atelomycterus marmoratus)*. I chose this shark because it stays relatively small and should live comfortably for at least two years in a 180 before needing a larger home.  Here's my question...
After re-homing my fish, corals and cleanup crew I  was recommended (by my LFS knowing my future plans) & purchased a Longspine Urchin (Diadema setosum)
<Mmm, I would not do this with a shark present in a system>
 to help keep the rocks and glass clean. My Catshark should be arriving this week, will I be able to leave this urchin in the tank or will  they harm each other?
<I would definitely remove it... use scrapers, nutrient limitation, water movement... macroalgal culture in a tied-in refugium on RDP... more gone over on WWM under "maintenance">
Thanks again,
<Welcome! Bob Fenner>

urchin question, comp. 10/10/11
Hello crew!
First and foremost, thank you for all of the information you've provided.
WWM is my first and favorite resource!
I have a question regarding a specific urchin. I have a 200 gallon reef set up, and I saw a strikingly gorgeous urchin at the LFS. My first instinct was that because it was gorgeous, and moved rather quickly, that it was probably bad news. :)
<Is toxic... to touch>
They were calling it a Purple Haze Urchin, which I found no information on. I am thinking it is Asthenosoma sp.,
which I found on WWM, but I'd like more information. (this urchin is rather flat; the other possibility might be Astropyga Radiata, but that one doesn't appear to have as much blue as Asthenosoma sp, and is not as flat.) Searching the internet, I've easily and only found photos and hosting inverts, but no concrete information. On WWM it is listed not safe with other inverts, and I do understand it is venomous. Can you expand on the diet/compatibility?
<I can not first hand, but from Baensch and other references, this includes macro-algae of various kinds, small animals and carrion>
It is unfortunate that this gorgeous creature is only $16, and that the LFS could not give me any real info. I'd consider it if I knew it might not touch my conchs, cucumber, sifting starfish, coral, and slower moving fish.
But, $16 is not worth losing an entire system over.
<Mmm, not likely to be problematical in a "large enough" setting>
Attached is a photo I found online of said species.
Thanks so much for your help!
<Thank you for sharing. Bob Fenner>

Re: urchin question 10/10/11
Thanks so much for your help, Bob!
<Certainly welcome Lis. B>

Coral banded shrimp vs. long spine urchin. 3/28/11
Okay... I just got a long spine urchin, before I got it I asked the fish store owner if my coral banded shrimp will bother it and he said no.
However, as soon as I put the urchin in my tank the shrimp immediately began to pull on the spines on the urchin. Should I get rid of one of these or will they be okay?
<? I would at least separate the two... now. Bob Fenner>
Re: Coral banded shrimp vs. long spine urchin. 3/28/11
How would I separate them?
<? A (chemically inert) partition, an all plastic "breeding net/trap", another system... B>
Re: Coral banded shrimp vs. long spine urchin. 3/28/11
I have a small tank, 20 gal. hexagon.
<Good for you. B>

Blue Pincushion Urchin vs. Lawnmower Blenny 12/9/10
<Hello Marie, and sorry for the delay in getting back with you.>
Does the Blue Pincushion Urchin ever kill fish?
<Not that I'm aware of.>
I had a Lawnmower Blenny that I really liked, but when I woke up on 9/2/10
I found him upside down on the bottom of the tank next to my urchin, looking very pale with purple where his dark brown was. (Not a nice birthday present for my son, since it was his 4th b-day. I didn't tell him.)
<Mmm, quite some time ago I see.>
All of my water parameters are good, according to my test stick and my salt level checker.
<Dip strips offer only ball park figures, would not rely to heavily on them.>
I only have a Horseshoe Crab (which is doing quite well, considering they usually don't get enough to eat, he has shed two times so far, and I have had him over a year. I throw extra food in there when I see him out and about, and I usually put frozen Mysis shrimp in the tank once a week.), a clownfish, and the urchin. The tank is a 45 gallon breeder tank, with live rock and sand. I had cleaned the tank a couple of weeks prior to my blenny dying.
He had been acting kind of funny prior to cleaning the tank. He started hanging out more away from the live rock and in the corner of the tank, whereas before he usually stayed most of the time hiding in the live rock or on top of it as his home. Then when I was cleaning the tank, he kept coming up close to the surface. I was scared he was trying to jump out, so I was extra careful to keep an eye on him. But, when I went in the bathroom to clean the algae off of the plastic filter parts, I forgot to cover the back area of the tank by the filter. I didn't see him anywhere when I came back, so I got worried he had jumped out. So, just to make sure I took out all 6-7 pieces of live rock.
I still didn't see him, so I thought for sure he had jumped out somewhere. I was really upset, because he was my favorite fish. (I had had him about a year.
The urchin we had just gotten in the last month or so.) While I was putting the live rock back in my tank, I heard something drop in the water in my cleaning bucket, but didn't think much of it. Then when I went to throw away the dirty filter from my bucket, I saw movement in the few inches of water in my bucket.
Apparently, there was a den in one of my live rocks, that I didn't know about.
I put him back in the tank and he didn't look or act hurt in any way. Then 2-3 weeks later he died. So, now I am trying to figure out if he died from some parasite he got before I cleaned the tank (but my clownfish didn't get sick), from getting hurt when I cleaned the tank, or if the urchin killed him.
(He had started to look slightly paler the last month or so.) Also, I was wondering if there are only certain types of algae that they eat, because I had started to get a different kind of algae on the rocks and less of the stuff that had been there before. I still had plenty of the algae on my glass at the back of the tank that he would leave all kinds of kiss marks on. I guess the reason I am wondering is because the urchin keeps going near to where my clownfish hides out, and I don't want my clownfish to die.
<No worries.>
Also, I would like to get some more fish for my tank, including another Lawnmower Blenny and a few green Chromis or some other type of schooling fish (preferably that won't jump out, when given the opportunity). (I am trying to be careful, because I don't want too many fish for my 45 gallon tank. So, if you have any suggestions, please feel free to offer them. I am a beginner, still.) My Petco, said that my urchin might have latched on to him when he was asleep, because he is slower moving, especially if he was sick. What do you think?
<Urchins are herbivores for the most part but are known to feed on animal remains.>
Should I take the urchin back, before I get more fish?
Urchins need a good supply of algae to survive long term so it wouldn't be a bad idea to return/trade it for something else if their food supply is scarce or you will need to supplement its food supply. Is likely the urchin was competing with your blenny for the same food source. Have you been feeding the blenny with any algae supplements?>
Could the urchin be stalking my other fish when he is hungry?
I think there is plenty of algae in the tank, but just wondering.
<Suggest reading here.
Also, what would be a good sand bed depth for my horseshoe crab?
Currently, I have about 2-3 inches of sand. He is currently about 3 inches across plus his tale.
<If you have had the crab for over a year, I'd leave well enough alone as they are generally short lived in captive systems. Most are cold water species that do not do well in the temperature range we keep our tanks at. May want to read here as well.
Since you are relatively new in this hobby, I will provide a link to our marine index which should prove very useful to you.
<You're welcome. James (Salty Dog)>

Atlantic Blue Tang ran into a Long Spine Sea Urchin 5/30/2010
I have a feisty Atlantic Blue Tang in my 400 gallon that ran into a large black long spine sea urchin. I could see the broken off spine protruding slightly from the Atlantic Blue Tang's head, and it has a chalk white circular ring around it about a 1/4" in diameter (please see attached pictures). First of all, should I remove the Atlantic Blue tang and try to remove it, or just let it heal on it's own?
<This latter. Leave this fish in place; the damage will heal of its own accord in time>
Secondly, what's the best way to get the long spine out of the tank without tearing down the tank?
<A grasping tool of length at night time, when it is out scouring the rock, bottom>
He is very fast and has grown very large.
Your help would be greatly appreciated.
Nancy B.
<Welcome. Bob Fenner>

Harlequin Shrimp And Urchins/Compatibility 3/11/10
Hi there!
<Hello Julia>
In a reasonably sized tank (100+ gal), could you house urchins (long spine and tuxedo) and a harlequin shrimp if the shrimp is routinely provided with meals? In addition to the chocolate chip stars there are also
LOTS of Asterina stars roaming the tank.
<First off, Harlequin Shrimp do best when kept as mated pairs. Although they feed primarily on starfish, they have been known to eat the tubed feet of some species of urchins. I am not aware of which specie of urchins these may be and Bob may input here re.><<Will try to eat most any/all. RMF>>
Thanks for your time!
<You're welcome. James (Salty Dog)>

Urchin eating Chaeto 2/16/10
I have had an urchin in my refugium for quite some time. It never occurred to me that the urchin may be the reason my Chaeto isn't showing the rapid growth that I've experienced with Chaeto in the past. Are urchins known to eat Chaeto? Love the site. Thanks!
<Mmm, yep. Bob Fenner>

Blue Linckia got eaten by my pencil urchin Linckia Systems\Urchin Behavior:
No Surprises here 11/5/2009

<Hi Maria.>
I found your site today and its awesome! Just to think all the money I could have saved if I would have researched properly before I purchased anything for my tank.
<Not to mention the lives of the critters...>
Here is my question I bought a pencil urchin about 3 weeks ago and he seemed fine in my tank that has plenty of live rock, two hermit crabs, a white sand starfish, and a clown fish. However, this past week I
bought a blue Linckia.
<Generally are doomed in captivity. read here:
http://www.wetwebmedia.com/linckiastars.htm >
It was doing fine until I noticed yesterday that is was hanging around the urchin.
And today I noticed that the starfish wasn't moving and its guts where hanging out. The urchin was right next to him.
Could the urchin have eaten him alive?
<More likely is the sea star died and the urchin is picking up a free meal.>
If this is the case then it must not be safe to keep in my tank. Please let me know if I should get rid of the
urchin and what starfish do you recommend I buy that will get along with all the animals in my tank.
<Fromia Seastars are generally much better suited to captivity. Have a read here: http://www.wetwebmedia.com/seastars.htm >

Pencil Urchin/Compatibility 2/27/09 To whom it may concern, <That would be James here.> Are Pencil Urchins considered reef safe? I've read that they are not considered reef safe. Is that true? <Indirectly, yes. They can be destructive to corals by causing rock slides which can fall on corals thereby damaging them. Any sponge and/or tunicate growth you may have will be at risk also. I would not introduce. James (Salty Dog)> Christopher Faiola
Re: Pencil Urchin/Compatibility 2/28/09
Salty Dog, Thank you for your response. <You're welcome, Chris.> I moved the pencil urchin that I've had for 3 yrs <no abbreviations please> into my Refugium. The refugium is full of algae and Caulerpa. That should make a good home for him? It took 3 yrs for me to finally realize that keeping one wasn't a great idea. I never knew they could be destructive. I noticed mine hanging over my corals. Maybe he was eating them? Hard to say thou.<though> I do own a Pin Cushion Urchin. That should be safe though right? <With caution as they do graze on live rock and can/could be destructive to organisms living on the rock. James (Salty Dog)>

Flesh Eating Urchin, Urchin Snack? 1/15/09 Hi Guys, <and gals> Good morning! <Hi Ginger> I searched WWM and couldn't find an answer to my question, so here goes. We have a 45 gallon tank, water levels normal. <Parameters normal?> We have live rock and a few fishy friends including crabs, a blenny, a goby, 2 clowns, a butterfly fish and an urchin. Last night we (including my ultra shocked 7 and 9 year old children) watched our butterfly fish swim right into our sea urchin, which we believe is a Diadema savignyi (Long Spined Sea Urchin). Of course, as you'd imagine, it was quite dramatic to watch what appeared to be blood spread where it had been poked and watched the butterfly fish swim around sideways and lay down at the bottom of the tank sporadically, as it (and we) awaited its death. Understandably, the children were very upset, and we used it as an opportunity to discuss ecosystems and how they work. After they went to bed, I waited for it to die so that I could remove it before the morning came, but it didn't. It actually had a few moments of normal swimming, and while I knew it probably wouldn't have survived until morning, I didn't feel right taking it out while it was still alive. I'll never forget the first thing I heard this morning when I woke up; desperate voices cried, "Mom, wake up! The urchin is EATING TAD! HE'S EATING IT! SAVE HIM!" I dragged myself downstairs to see, and sure enough, the urchin was on top of the now deceased fish and looked quite happy. Another ecosystem chat ensued, but fell upon deaf ears. My question is, should I allow nature to take its course, or should I remove our deceased friend to prevent the water levels from taking a turn for the worst? <I would remove the fish.> And by the way, I thought these urchins were herbivores? <They will eat meat if given the opportunity. The spines of this urchin are venomous so it did not surprise me that the fish died and do be careful when maintaining the tank, you will not like getting poked with their spines.> Thanks for the help; it's appreciated. <You're welcome. James (Salty Dog)> Ginger

Re: Urchin Snack? 1/15/09 Thank you for your quick response. <You're welcome.> We removed our deceased friend (over the strong protest of the urchin), as you recommended. Here's a picture of the victim after being lunched on for a few hours, just in case you wanted to add it to the story on your site for educational purposes... or is it too gruesome? <Should be fine.> Thanks again,
<You're welcome. James (Salty Dog)>

Arothron + Echinoid; no guesses for what happens next... 9/9/08 Hello WetWeb crew, <Hi,> i seem to be having a slight problem. my dogface puffer keeps taking bites out of my urchin. <Natural diet of these fish. Sea urchins are to pufferfish what mice are to cats.> i kept waving my hand in front of the glass whenever the puffer got close to him again but obviously i cant sit at the tank all day waving my hand. <Indeed not.> i like the puffer a lot and i also happen to like this urchin a good deal. the urchin has since covered itself in crushed liverock and seems to be hiding in the corner. should i be worried at all? <Well, "worried" is not perhaps the word I'd use. Arothron hispidus eats echinoderms, and indeed any and all mobile invertebrates. He'll thoroughly enjoy the tasty innards of the urchin, especially the ovaries which have a delightful texture and flavour. If you're concerned that the sea urchin shouldn't be viewed as live food, it will obviously need to be re-homed.> thanks for the help, -josh <One of those instances where reading before purchasing would have helped. Most any book should have made clear that combining Tetraodontiformes with the Echinodermata was asking for trouble (at least from the perspective of the sea urchin!). Cheers, Neale.>

My pincushion urchin. Echinoid comp. I just bought a black spiny urchin and I found my pincushion eating on it this morning when I turned the light on. Is there a reason why it ate the black spiny? <Mmm, hunger, opportunity...> I have 3 pencil urchins and the pincushion. I have a 55 gallon tank are there too many? <Apparently so> Thanks for any help Kelly <Welcome. Bob Fenner>

Question about Eucidaris metularia 7/4/08Dear Crew, <Andy> Hope you're doing well. I was wondering if you've ever heard of/witnessed a Eucidaris metularia (Ten Lined Urchin) munching on Acros? <Mmm, other Urchins, yes> I have a nice Acro. millepora on which I recently noticed small white patches. This is sudden, as the patches were not there yesterday. It does not look like necrosis or bleaching--rather the patches look like something took a bite out of the coral. I scanned my tank with a flashlight and could find no bugs in or around the coral that might be preying on it--I quarantine everything and give all my SPS a 10 minute iodine bath before placing them in the display. The only thing I can think of is that my urchin may have mistaken the base of the Acro for a snack? <Might have> I've attached a picture, although it's not a very good one--the lights were out. None of my other Acros have anything similar. Thank you for your help. Andy
<I'd remove this urchin. Bob Fenner>

Re: Question about Eucidaris metularia 7/4/08 Thanks, Bob. I will move the urchin to my 30g cube--no corals, just a Yellow Watchman Goby/Pistol Shrimp and a Pearly Jawfish. Have a good holiday weekend. Andy <Am off to hopefully move a hive of bees from a rental attic with a friend... Let's hope that moving this Urchin solves this mystery. Cheers, BobF>

Pencil Urchin/Compatibility 3/9/08 Do Pencil Urchins kill fish? <No.> I just bought a 55 gallon saltwater tank that has two Pencil Urchins in it and it also has two Pajama Cardinals. I bought a Lawnmower Blenny and a clownfish but my Lawnmower Blenny died. When I found him the urchin was munching on the dead body. At first I thought the blenny wasn't getting enough to eat. So I bought a Firefish Goby and I just found him dead and the urchin had already eaten half of it so I am wondering if the urchins are killing my fish? <No, you are.> Because those two kinds of fish seem to stay on the bottom a lot, and my other three fish are fine with no problems and all the basic water tests are fine (salinity, ammonia, nitrates, and nitrites). <Not necessarily indicative of good water quality.> I still haven't gotten the pH test kit so I am not sure about that one. <Yikes, should be one of the first kits to buy. Let's start by reading here and linked files above, and do get the pH test kit. http://www.wetwebmedia.com/watrqualmar.htm In future queries, please cap "i's" and proper nouns, saves us time if we do not have to do it for you. James (Salty Dog)>

Dead urchins 2/23/08 Hi, <Francesca> Thanks for all your help in the past, it has been invaluable. Unfortunately today we have made a fairly horrific discovery, two of our previously perfectly healthy urchins have been cracked open and the contents removed. <! Check the local sushi bar... Is uni on sale?> There have not been any very recent additions other than a pistol shrimp. The other possible culprits we have come up with are a zebra moray, a green brittle star fish or our sohal tang (we have many other fish but these seem the most likely from our research). The Moray has been in the tank for nearly a year so I think this unlikely. Are any of these known predators on urchins. <Mmm, not usually... are crab/crustacean eaters...><<Yikes... I stand, ok, sit in correction: http://fishbase.org/Summary/speciesSummary.php?ID=7880&genusname=Gymnomuraena&speciesname=zebra Gymnomuraena zebra DOES eat urchins... Sorry re. RMF>> The urchins in question are a blue tuxedo urchin and a purple pincushion urchin. We also have a long spined urchin who has so far been unharmed should we be looking to move him to another tank? What are the known predators of urchins in reef tanks? <Triggers, large puffers, some larger Labrids...> Thanks Francesca <Mmm, highly coincidental, but maybe the two urchins perished from other than predation? Bob Fenner>

Pincushion Urchin and Hermit Crab Compatibility - 1/31/08 Hi, <Hi there, Barb!> I have had a 25 gal marine tank for years. I have a clown-recently purchased to give my little green fish (sorry don't remember name of him) company, and a pincushion urchin (new addition). A friend would like to give me a dwarf yellow tip hermit crab, small at this time. <Clibanarius sp.> Will the crab and the urchin get a long OK? I have had several different hermit crabs over the years with fish, but never with an urchin. <They'll likely get along fine but it depends on which type of Pincushion Urchin this is. That's the problem with common names. This could be one of several different species. Please see these links for comparison/ID, as well as compatibility issues. http://www.wetwebmedia.com/urchinsii.htm http://www.wetwebmedia.com/urchincompfaqs.htm > Thank you Barb N. <You're very welcome. Take care. -Lynn>

Crab Removal and Tuxedo Urchin vs. Soft Coral - 12/13/07 Good morning, <Hi David!> I'm curious about the jar method for catching crabs. I took equivalent of a pop bottle, carefully peeled off the label and scraped off any adhesive... Then I boiled the bottle in a pot to sterilize it for 5 min.s. Once cooled down, the bottle was perfectly clean and hopefully sterile. I filled the bottom with about 3" of sand and placed 3 pieces of krill in it... The bottle is leaning up against the crab infested rock...48hrs... No crabs trapped. <Takes time, patience, right bait, and hungry crab(s).> The largest crab could fit into the bottle opening sideways. Do you think I'll have better luck if I use more sand to bring the bait closer to the neck of the bottle? <Can try this, as long as the sand isn't up high enough to allow the crab to grab the top edge of the bottle and crawl out. One possibility is that the krill just might not be "stinky" enough to lure him/them in. It sure would have been nice had the crab(s) gone the easy way and fallen for the jar trap! Since they haven't, and it sounds like the crabs are all still fairly localized, I'd consider removing the rock to a bare bottom quarantine tank and thus gaining the upper hand. One of the many good things about this is that you can control the food supply. When he/they get hungry enough, they'll go after whatever's in that trap. It also eliminates the possibility of your other inverts accidentally wandering in. The main advantage though, is that the crabs can't wander off and take up residence elsewhere in the display before you catch them!> This morning I spotted the large crab likely about 4" away from the Jawfish. <Hmmmm> The Jawfish didn't seem concerned and the crab was feeding on some Caulerpa. I have had emerald greens before without incident (mind you none were this big)... This crab looks identical to the emerald green Mithrax, except it is black with sandy brown legs. Would you say that any crab that's of decent size is likely risky in a reef tank with smaller fish? <Yes> He is kinda neat, but obviously I don't want to stumble upon a Jawfish carcass one morning. <No kidding!> If the 'jar method' for catching these critters takes too long... Do you think removing the liverock and placing in a bucket of tank water and putting some powerheads on the holes would drive them out into the bottom of the bucket without damaging the feather dusters and soft corals? <You could give it a try, but I'm thinking it's more likely the crab(s) will simply hunker down/go into an area of the rock that's not getting blasted. There's also a good chance that it could damage those soft corals. My next step would be as stated above: QT, control food, trap/net.> I have a fairy wrasse in quarantine and I suspect the wrasse will find this crab infested liverock that is so porous with a variety of large chambers within... Of particular interest for a home. Sleeping wrasse in liverock infested with a few small crabs and one brute... Ok, maybe I am answering my own question. Could be disaster? <Heeee! Yes - something along the lines of "Come into my parlor, said the spider to the fly!". Depending on the size of the wrasse, you might be able to block off/separate part of the QT with Eggcrate, or similar.> Lastly, I mentioned my small tuxedo urchin sitting in my soft coral tubular polyps. I believe he was just passing through. You had mentioned I should move him. Anyhow, when I came home from work all the polyps were open and no apparent damage and urchin seemed ok as well. This is two days later now, again last night Urchin was sitting in the polyps again. <Hmmmm> I'm wondering if you figure he's once again just passing through or... Can/does an urchin actually feed on corals? <According to what I've read, Tuxedo urchins/Mespilia globulus, rarely eat corals. They're mostly herbivorous, but if they ran out of algae/got hungry enough...? I'm a little concerned, about the repeated visits to the soft coral - unless it's dining on algae on the base/where it's attached. Would monitor closely for any signs of damage.> Anything I've read suggests they are totally reef safe. If no damage is being done I'd like to keep both... The alternative is to move the tuxedo urchin to my 200g FOWLR tank that houses a Snowflake Moray, Foxface, Harlequin Tusk, and soon to have tangs/Angel/trigger.... <Would monitor, relocate if necessary.> David Brynlund <Take care - Lynn>

Harlequin Tusk and Pencil Urchin 3/26/07 Hi Crew! I'd be lost without you! Long before making any purchase for my tanks I always research it on your site, and trust me, its saved many a fish, etc. <A pleasure to realize how we've helped you help your livestock> I've been searching for several days now, and can't find the answer to my question. I'm interested in getting a Harlequin Tuskfish. I understand he will likely eat my hermits (although they're pretty big) and will probably leave my Chocolate Chip Stars alone. <Mmm, yes... though it might sample these barely motile invertebrates as well> What I can't find out is if he'll sample my pencil urchins (Eucidaris tribuloides)? <Possibly as well, yes... Though if started as a small specimen, fed on a regular mix of foods, much less likelihood> I have a male/female pair (they spawned once--freaked me out, until I realized they weren't having fits) and have become rather attached to them. <Ahh!> And while I have your attention--would a serpent star or a brittle star just be an expensive treat for my Lionfish and/or Snowflake Moray? <Not likely... a very small possibility> They both gobble up squid tentacles like candy and I'm afraid they might mistake a serpent star in particular for this? What do you think? The lionfish was sold as a "Black Volitans" but he better resembles a Pterois russelli, if that makes a difference. Thanks so much, BC. <Welcome. Bob Fenner>

Pencil Urchin and Feather Duster Compatibility ...Not 1/31/07 <Greetings, Mich here today.> Thank you for your time and resources on WetWebMedia. <You're welcome!> I am having trouble finding if a pencil urchin and feather dusters are compatible. <Compatible in a "get in my belly kinda way". The urchin will likely feast on the feather duster.> I have found one article on the site about an urchin eating a feather duster the only advice I saw given to him was to use spell check. <Mmm, someone running low on patience, sorry.> My tank is a 46 gallon bow front with 60+ pounds of sand and 60 pounds of rock. <OK.> 1 Sand-Sifting Starfish 2 Clarkii Clownfish 2 Skunk Cleaner Shrimp 3 Dwarf Blue Leg Hermit Crab 3 Random Snails 3 Random Feather Dusters And plenty of life coming off of the live rock. <Very good!> I know the Sand-Sifting Starfish should be housed in a bigger tank. <Yes, prone to starvation and will take out many of the beneficial creatures who typically reside in the sand bed.> Back when I first started, I went my LPS and asked them for about 5 crabs of some sort for algae and they were out and recommended the starfish knowing it was a new tank. This wasn't just any pet store. It was a fish only pet store. <Bad advice can come from anywhere.> Anyways, are pencil urchins compatible at all with feather dusters? <Mmm, no. Regards -Mich>

Hair algae, P. diadema, and Zoanthid rejuv. 1/25/06 Hello folks, <Deb, glad you could join us.> Thanks so much for all of the helpful information. <We *try* to be helpful!> In the next 6 months, I'm going to be upgrading this tank to between a 150g and 250g system. At that point, I will make my 55g into the sump for the main tank. I will either section part of this off for a refugium, or I've got a 20g that I can hook into the system as a refugium. When I do this, my canister filter will go away, and I will be implementing a DSB in the main tank. Until I can do this, I plan to continue weekly 20% changes (replacing one section canister filter media each time), continue aggressive skimming with the CPR BakPak, and continue to ensure that the current in the tank is strong. <Very glad to hear that you are moving beyond canister-filtration. You will be moving into a much more versatile/useful configuration.> At this point, my Cyano problem has seemed to cure itself. In doing the weekly water changes, I found that the pump servicing my SQWD system was clogged. This was inhibiting water flow significantly in the tank. Now that I serviced it, there's a pretty strong current in the tank, which probably helped to eradicate the Cyano growing in the tank. <Most likely, this helped a lot!> Also -- my Halimeda is making a comeback, though I still need to continue cleaning hair algae off of it every couple of days. The bubble algae is still present in the tank, but somewhat manageable, as I can gently pull it out during water changes and dispose of it. <Are you sure you have bubble-algae? Sometimes, I think folks think BGA is bubble when it has gaseous packets in it's layers...> So, the only real problem in the tank is the hair algae. It's still growing quite rapidly. In trying to fix this problem, my bicolor blenny stopped eating and has "disappeared" in the tank. <Maybe he needed a vacation. Heck, if I had to eat hair algae...> I'd like to pickup a lawnmower blenny to replace him and to help with the hair algae problem. <Remember, Deb: This is dealing with the symptoms of a water-quality issue. IIRC, your last phosphate test was .03ppm, and I was asking how sure you were of the accuracy of that result. Where do you stand now? Did you ever buy a new kit?> Once the hair algae is gone, I plan to supplement his feeding with various algae foods (as I already do for my Coral Beauty). <Should pose little problem with a little research...> Adding him will result in having the following fish in the tank: 1 coral beauty, 1 Dottyback (Pseudochromis diadema), 1 yellow-tail blue damsel and 1 lawnmower blenny. Does this seem like a sound decision to add this fish? <As long as you aren't hoping for a total massacre on the hair algae, yes. In my experience, algae-eaters always choose to ignore the one thing you bought them to eradicate.> Otherwise, my Zoanthids have stabilized a bit. They're not dying off anymore, but they're not flourishing as they've been for the past few years. Only a handful are opening up, and not fully at that. <All this points to a water chem. issue to me.> I'm hoping that they are on the road to recovery. I'm supplementing the daily feedings now with Cyclop-Eeze, in hopes that the added nutrients will encourage their growth. I also use a plastic turkey baster to blow water over them with each water change to try to free them of the hair algae that grows around them. I've ordered new test kits for my phosphates, silicates and nitrates, and they should be arriving any day now. <Ahh, very good. A reputable, reliable manufacturer, I hope. Mmm, one note: Silicates aren't a factor unless you have huge diatom blooms, so worrying about the concentrations is moot IMO. I don't own a silica test kit.> I've taken the water changes down to 1x per week, 20% using RO/DI water. I've just gotten new cartridges in for the RO/DI unit and will be replacing them this week. I've also cut back my lighting schedule, taking 1.5 hours off the back end for both the daylight and actinic lighting. <Good steps, all.> In doing all of this work, I've realized that I haven't replenished my cleanup crew in years. I've still got about 10-15 Astrea and turbo snails in the tank, but all of the small crustaceans are gone. I'd like to replenish this crew, but am afraid that any crustaceans I add will be decimated by my Pseudochromis diadema. Any ideas on what types of inverts I can get to replenish this crew that will survive the presence of the Pseudochromis diadema? Having a well stocked cleanup crew may also help with the algae problems in the tank. <Hmm... I never worried about a P. diadema bothering hermits to the point of murder. Types and compatibility of hermits is not a strong-suit of mine, but I know we have the info here on WWM if you look for it.> So, to summarize: -Lawnmower blenny for this tank -- good or bad idea? <Good, in your case.> -Any ideas on how I can nurse my Zoanthids back to health? <Provide optimum water conditions: temp, movement, quality, feeding, lighting spectrum/duration.> -Any ideas on how I can supplement my cleanup crew without buying an expensive smorgasbord for my Pseudochromis diadema? <Mmm... *I* don't see a problem with the "generic" red-legged hermits here. (RMF strike me down if I am in error)> Thank you so much for all of your help. <Oh, Deb. You know we love you. -GrahamT> Deb

Chocolate chip ate my urchin? 1/6/07 Hi, <Good morning, Joanne. Graham T. with you today.> Is it a known fact that if you put a chocolate chip star fish (sea star) in with a urchin the chip will eat the urchin? <CCS will eat a *dead* urchin, sure. Probably dying, but not a healthy urchin.><<Mmm, depends on relative health, hunger. RMF>> Why I ask? I know nothing about salt water tanks so when we purchased a home with two big built in tanks we hired a 'fish man' to take care of them. <Good idea to get some help up front at the first...> To make a long story short, one tank needed to be treated <For what?> so the 'fish man' took out the urchin and chip (who had been living together in a big tank) and housed them together in a small tank while treating the tank for a week or so. <Possibly, the urchin was already hurting when moved. Although you don't mention what "brand" of urchin you are mourning, I don't know of any CCS predating them.> The next morning the chip was on top of the urchin, which by now was dead. <If you don't see it happen, don't assume the CCS is a killer.> Should they have been put together in a small tank and should the 'fish man' have known this would happen. <That is hard to say, but I question whether they saw any medication before they were relocated, how they were relocated, and also how closely the tank conditions in the smaller tank match the larger one. There should've been no problems with the two eating each other, however, when either Echinoderm gets hungry, they eat what they can "catch", which may include dead and dying specimens.> Thank you. Joanne Cork <Good luck with your systems, and the treatment, too. Hopefully you aspire to eliminate the "fish-man" eventually..? -Graham T.>

Echinometra mathaei? 12/8/06 Crew, <Chris> I feel guilty as this is about the fourth time I've emailed you guys, and I know from cruising through your site frequently you must have a MASSIVE amount of email daily. <Mmm, not too/that much... thankfully. And many good friends to help in responding> I utilized your search tool on Echinometra mathaei and couldn't find my answer....... <An accumulation of collective experience, reflection, facts, methods... even in "just" ornamental aquatics is a several life-time endeavour... We will never be "finished"> I've got a 65 gallon reef tank with a fairly new (about four months old) DSB refugium (about 30 gallons on a RDP light cycle). Reef seems to be doing pretty well, and the refugium is packed full of microcrustaceans (so is my tank!!!). Also LOTS of fine green hair algae in the refugium, not sure that that part is good......though the pods like it. On to my question. At some point I realized that I had a nice little live rock hitch-hiker in my main tank; a neat little urchin that was about the size of a pencil eraser. <Evidence of good live rock, processing, your care...> I've watched it grow to about the size of a quarter (diameter with the spine length included) within the last about 8 months. It comes out mostly at night, is black with an oval body, and has white rings at the base of the spines. From what I have researched in books and on your wonderful site, I believe this to be an Echinometra mathaei. <Possibly> I understand from what I have read that these guys are not reef safe and can be rock drillers. <Mmm...> It doesn't seem to be doing any damage yet, and I'd just as soon leave it....but I guess it leads me to three questions: 1) Will I ultimately have to remove him from my tank (I have some xenia colonies, a mushroom colony in the front corner of the tank, a couple of small Zoanthid colonies, a branching Montipora frag, some star polyp colonies, a Pavona cactus and a yellow toadstool). <Maybe> 2) Can I put him over in the refugium? <Yes... esp. if there's a bit of rock for habitat...> This refugium harbors nothing other than pods, two small turbo snails, and a feather duster. Eric R. has advised me in the past to not put stars, urchins, etc. in there. I've heeded his advice diligently. Can this one little guy corrupt my refugium or is my best alternative to give him away? <I would keep this animal if you had interest... Echinoderms, I find, are a bit "mis-understood"... perhaps due to their slow movements, largely reclusive/cryptic lifestyles... many are outright "determinant" species in their habitats... largely determining... through predation, their presence in other ways... the make-up of other biota... But this echinoid species/specimen... in a captive setting... I think of as not too overly destructive> 3) I've heard some urchins can be toxic. Can I safely remove him, without killing myself (kidding...........sort of...... :-) <... I would leave it outside to dry if this were your intent> Thanks in advance you guys really make an amazing contribution to the hobby. Chris <As are you here by sharing. Bob Fenner>

Urchin... comp. & as scavengers mostly 12/2/06 Good afternoon. <And to you, Mich here.> I recently purchased a variegated urchin (Lytechinus variegatus) at my LFS to assist in some algae control, and there were 2 color morphs, a green variant and a pink variant. The store owner talked me into choosing the pink for it's brighter coloration, but when I brought it home, it took much greater interest in my pink coralline algae than in the green hair algae I was intending for it to help with. I realize any urchin will likely have a taste for coralline, but does the animal coloration have anything to do with it's dietary preference? That is, if I had chosen a green one, would I be having more luck with the urchin devouring my green hair algae? <Unlikely. As you know, most urchins will eat coralline along with other desirable organisms ...they are not really reef safe.> Thanks...<Welcome> Tim

Urchin question 8/20/06 Hello WWM Crew, <Sara> I have a few of questions regarding a Lytechinus variegatus urchin ( I was able to id from your site), I hope you can help me out with. My first question is if a Lytechinus variegatus urchin is in the process of dying, or not doing very well, is there any chance it could release toxins in to my tank? <Mmm... yes... this species is a member of the Family Toxopneustidae... toxic to even the touch... to fishes, humans> Should I remove this urchin from my main tank? <Unless it were very large (hundreds of gallons), exceedingly well circulated and filtered I would not introduce a member of this family> I had noticed that my urchin had been losing spines at an alarming rate recently and had stopped moving around the tank. When I turned him over there was a brown/tan worm on him. This worm was not a bristle worm, rather it looked more like a common earth worm (only much, much smaller.) It had small bristles on it's side, but the bristles were not near as large as a bristle worm's. <There are actually thousands of different species...> I also have noticed that there are deep red spots on the outside of the urchin it almost looks like blood. After I removed the worm from the urchin he immediately improved and began to slowly move around the tank again. So, I guess my main questions are should I remove this urchin from my tank and quarantine him? <Yes, I would. Don't use your hands in contact... scoop into a container... i.e., don't expose to the air...> Is there any risk he will poison my tank if he dies or is dying? <Again, yes> Lastly, are there any know worms that are parasitic to urchins, or was this worm just a result of him dying/not doing well? <Could be either/both> Thank you so much for your help, Sara <Welcome. Bob Fenner>

Help - Hatpin Urchin Question 6/3/06 Hi, <Hello there> I have a problem that I cannot find a definitive answer to in the FAQs and would like to pick your brains about the possibilities we are facing. My partner and I have a three-month old forty-five gallon FOWLR tank that was cycled with Damsels, which were returned to the pet store after the cycling was complete. <Mmm, there are better methods...> The tank tests clean with the following results (we test twice per week): SG 1.0025 <Off by a decimal place> Temp 82.3 (regulated) Ammonia 0 Nitrites 0 Nitrates less than 5 PPM (we change the water twice per week to keep these as low as possible) Phosphates near zero Calcium 500 PPM <Too high...> CO2 0.7 PPM, Copper 0 PPM After the damsels were gone, we slowly added our invertebrate livestock before we added our fish namely because it was easier to do it that way: 1 hatpin urchin (diadema setosum), 1 pencil urchin (Eucidaris tribuloides), 2 cleaner shrimp, 1 blood shrimp, 12 hermit crabs, 4 turbo snails, 1 queen conch and a chocolate chip starfish. <This last is hard to keep in new systems> These guys were added starting about a month ago with the Starfish and ending with the hatpin urchin. All have been doing exquisitely well and all were researched extensively before we purchased them so that we weren't making any mistakes that might cost an animal its life. <Good> Last night we put our first fish into the aquarium: 2 Banggai (sp?) cardinal fish, 1 Tomato Clown and 1 Flame Angel. <Forty five gallons is too small for this last> Again, we researched all three species to make sure the tank was big enough and that they'd coexist peacefully before we bought them. We drip acclimated them over a 1.5 hour time period, fresh water dipped them and then added them to the main tank. We didn't quarantine as they were the first fish in the tank <So... you've forgotten re the damsels...> and we'd read that for the first fish, quarantine isn't necessary. <Incorrect> (After the damsels were gone and before we put the inverts in we heat treated the tank to accelerate the lifecycle of any parasites that might have been left over from the Damsel population). After they were in the main display, everything was fine. They were stressed for a bit but quickly took to the tank, swimming and roaming: all were healthy. We shut the lights off and left them in the tank with the lights off over night and this morning at lights-on we fed them and they all ate fine including the flame angel. All morning the angel was foraging and swimming about and looked extremely healthy and vibrant; her colours were glorious in the tank. The last time we looked at her was around 1:30 today and she still looked fine. We left on an errand and when we came back she was inside her little cave that she'd occupied. The cave that she chose is inside and backs up to the space that the urchin calls home. About two hours after this, we noticed she was lying on her side in the little cave. She was still breathing but in hitches and she finally died and when we took her out, her colour was almost completely gone -- she was almost white with very little orange left. We examined her closely and noticed a small white spot on one side that looked very much like a puncture wound. <Possibly> Our theory is that she got too deep into the burrow and was punctured by the urchin or that Vlad (the blood shrimp) was trying to clean her and possibly pushed her into the urchin. The burrow where she died is also where the blood shrimp hides during the day and has his little cleaning station. We knew when we got the Urchin that it was venomous but everything on the WWM that we read said that fish would stay out of their way <Almost always do> and there were even articles on the site of fish getting poked and spines dislodged in them that didn't die. Given all that information, we thought the Urchin was a safe buy or at least that we were able to keep him with fish . . . now we're not so sure. <Not likely the primary cause of loss here.> Here's my question: If the Urchin poked the angel (I'm 99.99% certain that it did; I saw the wound) could its venom have killed her? <Mmm, not likely by itself, no> This is very distressing because we love the urchin, it is a beautiful animal but we love the fish as well and we are in process of trying to decide whether to keep Spike or return him so that we can safely keep fish in the tank as that was our ultimate goal to begin with. We're also very concerned about the Cardinals and the Tomato Clown getting punctured by him and dying of his venom if that is the cause. <Not likely to poke these> Any advice would be most helpful. Warm regards, Dennis <More likely "cumulative stress" at play here in the loss of the Flame Angel... a hard go before your acquiring it, being placed in a very new system, crowded with the Tomato Clown (keep your eye on this... alpha fish here). I would take a long term view and leave off with other livestock additions here for a few months. Bob Fenner>

Urchin Compatibility - 05/10/2006 My friend is getting rid of a Tripneustes gratilla and the only problem I have seen in his tank (other than eating unhealthy soft coral) is that it likes to carry small rubble around. <Normal trait for the Hairy Pincushion Urchin.> After reading a lot of the faq's I learned that it is venomous to the touch. <The tips of all urchins are somewhat venomous but pose no serious threat to humans unless you are one of the few people who are highly allergic to bee stings and the like, however, it is toxic to the touch for sea life.> I couldn't find the answer to this question in the faq's or on the forum (hopefully it hasn't been asked already) Will the urchins sting harm coral?? Or fish? I have two different species of xenia sps and LPS corals mushrooms and Ricordea. Thanks for the help. <You're welcome. James (Salty Dog)>

Urchin and Reef Compatibility……and Adam J Be Quiet and Get to the Point!! - 4/24/2006 Just a quick Q, <Lies and Blasphemy……just kidding.> What's the consensus on urchins in live rock or reef tanks? <Consensus? Reef Aquaria? My friend, especially after attending WMC….I don't think the word consensus belongs with the any type of aquaria. Not only are their varying opinions among aquarists…including the experts, but there are many variables period. My reef tank may not be your reef tank, and what I mean by that is what type of animals do you keep, wish to keep (What is important to you?) Furthermore there is varying behavior and diet amongst species. Mike Paletta expressed a heavy recommendation for urchins in his pitch at WMC while I know many their reputable aquarists who would by no means utilize them. Personally I keep a small diadema urchin in my tank, thus far, (I repeat)…thus far no problems with any predation on sessile invertebrates, however he is quite clumsy and knock things over at times………and he may have to "GO" for this reason eventually, at the moment he still intrigues me in his own right.> I put a few black Caribbean ones in, and they are great at scouring any algae, should I be worried about anything else ? <In my experience they are fine, and I presume they are small for you to say a "few", just keep an eye on them as they age….sorry for the ranting…been a He!! Of a weekend - in a good way though.> Thanks, Steve. <Anytime, Edward - .......I mean Adam Jackson.>

Sea Urchins and Xenia 2/22/06 Dear Madam or Sir: <"Paperback writer..."> Thank you again for your assistance with my aquarium. After reading a few books, and pestering my local merchant, I recently purchased some Xenia. The folks at Norfolk, VA's Colley Avenue Corals (a new store, if I may give them a shameless plug) spent hours with me as I examined their tanks and asked questions about basic compatibility, temperature, lighting, water quality, etc. However, I never thought about inquiring about sea urchins. <Okay> I have three sea urchins in my 55-gallon tank. I believe they are either Echinometra lacunter (rock boring urchin - based upon the description and picture on your web site) or Echinometra mathaei (common urchin - based upon the location from which the live rock was collected). <Both common> They are about one-inch in diameter and appear as active during the day and night. The tank has been up about one year, and they are probably 50% larger than when I started cycling the water. At least two of the urchins seem fascinated with the Xenia. They appear to crawl right up to the stalk. It could be the rock has some algae on it, or it could be they see an enticing and expensive treat. <Mmm, possibly> I've tried to scoot the urchins away with a turkey baster, though this may upset the Xenia almost as much as being munched upon. One of your FAQs (around NOV 2004) the following note about a diadem sea urchins and Xenias, "I'd say he is running out of good algal food, and this is his next choice. I would feed him some Nori sheets...It may be a case where it is starving." Unfortunately, the fish (and urchins) ignored the Nori sheets I used to place in my tank. And I know the offenders are not diadem urchins. Negative reinforcement does not work well with our cat (or our children), <Nor me> so I don't hold too much faith in the turkey blaster training regimen. Assuming I want to keep the corals, should I look for a new home for the urchins? <Possibly... sorry for this apparent vagueness... it may be that the urchins will leave this pulsing soft coral alone... not actually eat it, but could cause problems with "poking"> Or are they simply looking for algae in all the wrong places? <Mostly this> Will these urchins grow too big for the tank, and therefore need to move to a classier neighborhood anyway, relieving me from this guilt? <Yes...> Thank you for your help. Sam <Thank you for writing. Bob Fenner>

Goby With Urchin Spine Through Its Head! - 02/12/06 Hi, <<Hello>> We have just discovered that out new little goby (3 weeks in tank) has a spike through his head from our urchin (see photos). <<Yowza! More than 30 years in this hobby...first time I've seen anything like that...>> He does not seem to be distressed and is feeding and swimming as normal. <<Hmm, must have not struck anything 'vital'.>> Since the photos he has banged his head around on a rock and taken both ends off - we can still see the spike inside. Is there anything we should do or should we just observe? <<I would be inclined to leave things as they are. If the spine has not killed the goby by now, catching/handling it to try to remove the spine will cause undo stress or even kill it outright. Many thanks
<<Regards, EricR>>

<Shades of a Steve Martin skit!>

Urchin mysterious death-poisoning of tank 02-05-06 Dear Crew, <Dawn> My tank recently crashed. Most everyone was saved, except the fish, who perished very quickly. It happened while I was at work; my housemate reported tank looked great at 3pm. It was cloudy / milky by the time I got home 3.5 hours later, fish were dead, and most everything else was severely stressed. I suspect the death of a Diadema setosum or Antillarum (not quite sure which it was) is what triggered the crash. <Could, yes> I think it died, (it hadn't been well for some time, it had dropped it's spines 3 times in recent months), and in turn created a toxic soup that caused tank crash. I do not have good facts for this, just my suspicions. I've been researching for info re: toxicity of urchins in the tank once they die, but having very little success. I did find this on WWM, but little else in the Urchin articles and FAQs - "There are no absolutely reef safe urchin species IMO... too much chance of mysterious death-poisoning of the system" ~ Bob Fenner. My questions: What leads Mr. Fenner to the above conclusion? What can you all tell me about the death of sea urchins poisoning a tank? Could you point me in the direction of additional information? Thanks in advance and kind regards, Dawn < http://www.google.com/custom?q=urchin+poisoning&sitesearch=wetwebmedia.com Bob Fenner>

Re: Urchin mysterious death-poisoning of tank 2/6/06 Thank you for your quick reply. <Welcome> I had done that particular search (and others as well) on WWM and read the articles / FAQs that came up prior to posting my question. The first hit on the search results is the one from which I drew Mr. Fenner's quote. I have in addition done much looking on the web, thinking it must be common enough that I would find many sources of info. There is a great deal of info surrounding being poisoned by mechanical injuries involving urchins, but I am having difficulty finding info about the death of an urchin poisoning a tank. I've also approached local LFS', all of whom profess they've not heard of such a thing as a dead urchin poisoning a tank. Would it be possible to give a quick outline of your understanding of the issue of urchin death poisoning the tank? Thanks again, Dawn <Just this: that these events are positively correlated anecdotally. Bob Fenner>

Re: Urchin mysterious death-poisoning of tank 2/7/06 Dear Bob, <Dawn> That's a quick outline for sure! Thanks much. Scientific analysis generally tells us what we knew anecdotally. I appreciate your feedback. Regards, db <I welcome your candor, response. Bob Fenner>

Urchincide... Is It Necessary? - 12/18/05 WWM Crew, <<Ken>> First of all let me say thanks for the wealth of information available on your site. I have spent many hours reading Q&A on many subjects. <<Ah, excellent!>> What started out as a couple of small Diadema Urchins, has now multiplied into at least ten, large, Diadema Urchins. <<Golly!>> What is the most humane way of disposing of these creatures? <<!!??>> My concern is as the urchin's get bigger, more coralline is being consumed. Thanks! Ken Santa Rosa, CA <<Well Ken, your concerns are valid...more/bigger urchins will definitely equal more/bigger food consumption (assuming enough is available). But unless I'm misinterpreting your message, why do you feel you need to kill these creatures? Why not take them to your LFS for donation/trade/store credit?...donate to a public aquarium...sell/donate to a local aquarium club?...offer them up on EBAY? Put forth some effort to save these creatures...much better solution for our hobby (and the urchins) my friend. EricR>>

Diadema setosum and corals 11/2/05 I have had a 55 gallon fish and (non-photosynthetic) invert tank with live rock for four years and recently upgraded my lighting in anticipation of having a full blown reef. I have what I believe to be a Diadema setosum urchin. This urchin is black with long spines and an orange anal ring. It has done well in my system for four years and grown a lot! <Neat> I recently purchased a small frag of soft coral, a toadstool leather. Well, the urchin ate the frag. <Happens> He sat on it and ate it until it was completely gone. My research indicated that these urchins did not eat corals so I was surprised. I understand that these animals are individuals, however, so I guess I have a rogue soft coral munching urchin. At this point, after shelling out the bucks for the upgraded lighting I don't have any immediate plans to start up another tank to move the urchin into. What are the chances it would consume other corals with stinging capability such as LPS? <Small, but possible> Or a bulb tipped anemone? <Even smaller, remote> Could it be trusted with a clam? <Unless very hungry...> This darn critter has put me in a bind since I worry now about putting corals in the tank only to become an expensive meal for my urchin! <Constant vigilance... is not only the "price" of democracy/freedom (watch out America!), but the mixing of organisms in captive marine systems. Cheers, Bob Fenner>

Sea urchins just ate my feather duster and leather coral... poor English, lack of planning 9/28/05 Hello. you have a very informative site. I love it. I have 2 pin cushion and 1 pencil urchin, the other day, I noticed the pencil urchin was on top of the feather duster, and I didn't think anything about it. the next day he was still there, so I pulled him off, and the feather duster was just a pile of mush. his pipe was all soggy and it just fell apart. there is a small piece in there still, but I am positive it is dead. I sat the urchin in the back of the tank. later that day, I looked at the tank, and he was on top of a small new sprout of leather finger coral. now that im <There is no such word> paranoid, I moved him and he ate it too! it was gone! so now im constantly moving them around, the pin cushion ones too. cause im worried. I always keep a leaf of romaine lettuce in the tank, ok the glass w/ a veggie clip, and the LOVE it. they will devourer a leaf in a matter of hours. so any advice about the urchins eating my duster and coral? <Learn to spell, use your grammar checker to learn... and use resources ahead of time to check the compatibility of the organisms you intend to buy. Bob Fenner, too short of patience with ignorance today>

Would a pincushion urchin work with my tank? 8/31/05 Alright as of right now I have many assorted corals (soft corals) finger leathers, toadstools, Purple Plum, Pulsing Anthelia, assorted zoos and polyps. I also have a green bubble tip anemone and a LTA (getting read of him soon). As for fish I have a yellow tail damsel a 3 stripe damsel, a lawnmower blenny and red striped high fin goby. For inverts I have blue leg hermits, peppermint shrimp, pistol shrimp, emerald crabs, sally lightfoot crabs, a sand sifting Cuke, 2 serpent stars and 1 brittle star, Mexican turbo snails, Nassarius snails, Astrea snails and micro fauna of sorts and some Featherdusters. I was wondering if the pincushion urchin on ETropicals website would be an alright urchin to get and if it would be destructive of anything? <I would not place an urchin of any species in with this mix... too likely to spike the sessile soft-bodied invertebrates. Bob Fenner>

Urchin being consumed by an anemone Hello, I just got home from work and my green carpet anemone which I have had for 1 year now has got my sea urchin. I tried to pull it out of the anemone but it wont move, the anemone has a firm suction on it. what can I do? will my anemone eat my sea urchin? if he does what about the sea urchins spikes, wont it hurt the anemone . this is really stressing my out.....:( thanks for your help <At this point... leave it... the anemone will either ingest it or release it... Bob Fenner>

Pin Cushion Urchin partially eaten by Chocolate Chip Starfish I recently introduced a purple pin cushion Urchin (I think it is a Strongylocentrotus purpuratus) into my system. <I hope not... this is a cool/cold water species> Last night I came home to find my chocolate chip star treating him like a happy meal. There is a 1/2 inch section on the Urchin where his needles have fallen off or been digested. I have removed the star fish from the system and placed him where he can do no harm. The Urchin is understandably stressed and has not moved much (but it is still alive). My question is does this guy have any hope of survival and what can I do to enhance his odds of visiting the big reef in the sky? <Mmm, really just keeping the system, water quality optimized and stable, providing foods...> Thanks in advance and this web-site has been and continues to be invaluable. -Rob Glentzer <Rob, do try to ascertain the species here... Ask your source for its identity, look over WWM re... CCS are "not detritivores"... Bob Fenner>

Urchin now eating corals? I have a diadem sea urchin I've had for years and recently he has been munching on some of my new soft corals. (pulsing xenias and a type of tree coral). The corals where healthy otherwise, but I've seen the damaged parts he munched on. Not something I expect from a Diadem. I've had him for years and he has gotten along fine w/ the mushrooms, bubble coral, anemones, et al. << Indeed a little bit odd. I'd say he is running out of good algal food, and this is his next choice. I would feed him some Nori sheets, or maybe even ask a friend to take it for a while. It may be a case where it is starving. I've never seen any urchin eat soft corals in the aquarium. >> << Blundell >>

Hungry Urchin? (11/21/04) Hi <Hello. Steve Allen with you tonight.> I've been reading your brilliant Marine section for months & wonder if you can help with an urgent problem. Our reef tank is about 6 months old. One of our early purchases was a lovely little black spiny sea urchin. He helped clean up the tank as it cycled & settled down. We have very little "nuisance" algae now & are beginning to wonder is "Spike" is hungry... <I'm not sure if they get "hungry" per se, but rather they eat anything the deem edible that is in their path. The pretty much eat all the time.> Two nights ago he ate our small but healthy pulsing xenia, last night he had a go at the Gorgonia. <Did you see it eat these or are you guessing?> We always have seaweed in the tank for him, the Mithrax crabs & the tangs (& most of the other fish who also seem to eat it) which he seems quite happy with in the day but obviously gets bored with at night. We have only recently started putting soft corals in the tank although have had green star polyps in the tank for about 4 months - he's shown no interest in that! We think we're going to have to take him back to the LFS unless you can suggest any other solution. Any advice welcome. <If the urchin is eating these desirable organisms, your only option is to take it back. There is no way to compel or persuade it not to.> Thanks, Mandy Thomas <Good luck.> Urchin Spines (10/3/04)) Thanks Steve. The orange thing is on the top. I assumed it was an eye because it moves around like it's looking at everything. <That part is the anal sac. Urchins have light-sensing organs that are not true eyes (with pupils & such, like fish do).> It's in a forty gallon tank. If my fish are stung will they die or will they be stunned? <I would expect a smaller fish to perhaps die, but it is not really likely that a fish will run into it, unless startled. I am not aware of reports of this urchin killing fish. Hapless aquarists have been injured. Thos spends (if we're really talking Diadema) get really long (>6"). I really think you ought to consider Mespilia globulus as an alternative, although getting that Diadema back out could be tough.> I have a Percula clownfish, a green Chromis, Firefish, scooter blenny, some polyps and a Kenya tree, along with some crabs and snails. <Sounds nice.> Will it be okay to keep or should I get rid of it, with what I currently have? <The maximum size of the body is about 4" and the spines can grow up to a foot long. I would not want one in a 40G tank if it was mine.>

Urchin Tankmates (7/4/04) I had trouble sending a more detailed e-mail earlier, so here is the short version: I am setting up a 46 gallon bowfront marine reef aquarium with an EcoSystem 60 Refugium as the primary external filter. <Skimmer too?> I have about 28 lbs of live rock which was "fully cured" at the LFS, and 40 lbs of live sand (less than 1" deep on the advice of Mr. Leng Sy.) I have a Lemon Tang in to cycle the tank and the tank was set up 9 days ago. I am feeding Nori in a vegetable clip which I change every 12 hours, some Formula 2 once a day and some Kelp Flakes once a day. Ammonia has been running around 0.25 ppm and just yesterday I started getting a bloom of rust algae all over everything. <This is a phase. It would be nice to see that ammonia going down soon--can't be good for the Tang.> I intend this tank to be a species tank for 1 Orange-eye Urchin. <I am unfamiliar with this name. Do you have a species name? Is this to be to he only thing in the tank? That's what the term "species tank" implies.> I expect to move the Yellow Tang to a six foot long 155 gallon bow front in October after I set it up. It will have a 5" DSB, 2 protein skimmers, 2 refugia, and a sump. My immediate question is: should I get a Reef Cleaner package group of organisms such as small hermit crabs, snails, tiny brittle stars, etc. to add to this tank for control of the algae or will having the 1 Urchin in their be enough? <Brittle stars do not eat algae, and are useful for detritus removal. Experience with hermits for algae control is mixed. Urchins are voracious eaters, so I see no reason to have competitors. Secondary questions are: which corals will survive in a tank with the Urchin, and would 1 Tomato Clownfish and his anemone be fine in there? <No one on this site recommends mixing corals and anemones in the same tank. You can search the FAQs for explanations as to why this is so. It is also the consensus that anemones are difficult to keep and require a lot of light, so are best avoided by other than experienced aquarists. Being uncertain as to what species of urchin you are referring to, I can't make much recommendation on corals other than to point out that most urchins eat mostly algae. Remember that clownfish are perfectly fine without an anemone.> Laura L. Hammond <Hope this helps, Steve Allen.>

- Urchin in the House - Thanks for the reply. <My pleasure.> With respect to your sea urchin recommendation. Are there any issues with having an urchin in my tank with my livestock?? black brittle star cb shrimp & cleaner shrimp two gobies two clown fish Fire Goby hermits and snails??? <Should do fine with all these.> Don't the urchins get big? <Some do, but usually very slowly. The one I recommended is short spined and not very large.> I've heard of them knocking over liverock, etc...? <Not to worry, the Tuxedo urchins are a fairly tame bunch. Cheers, J -- >

Urchin Compatibility (1-13-03) I was wondering if I could add a few little sea urchins in to my tank with an emperor angel, orchid Dottyback, a green chromis,3 cleaner shrimp and a chocolate chip starfish? are all these compatible?<You should be ok, but I would probably only add one depending on the size of your tank. You can read more on these guys at our website www.wetwebmedia.com. Cody>

Green urchin Dear WWM crew, I have bought an urchin that I believe is a green urchin, that was labeled as a pin cushion in the shop. My problem is that it seems to be taking an unhealthy interest in my blue hermit crabs and snails, picking up their shells. Should I be worried? Is it venomous? It has a white body, with green spines changing to purple at the tips. It has 5 main white segments, and 5 smaller white segments in between them. Any idea what it really is? <My best guess from your description is a Lytechinus variegatus, harmless, but be sure to double check me here http://www.wetwebmedia.com/urchins.htm> Thanks in advance, James <You are welcome. -Steven Pro>

Safe Urchin? Dear WWM crew, Thanks for the reply. I think you are right, it is a Lytechinus variegatus. Please could you tell me if it is venomous, and if so how bad it would be for me if I got stung. Is it the spines or the podia that are venomous? Many thanks, James. <James... as Steve mentioned, it is harmless. Lytechinus is known as a collector or decorator urchin for its habit of collecting bits of debris to cloak its visage on the reef. It feeds mostly on algae but will accept meaty foods. Once established, it is a useful and innocuous aquarium inhabitant that is quite tolerant of its own kind. It poses little or no risk to corals as a predator but may knock specimens over clumsily. Best regards, Anthony>

Urchin & Crab Hey guys- I got a fairly large red hermit crab, has black hairs, white spots and fits in a large Mexican turbo snail shell. my question is, I picked up a small "orange eyed" black urchin, and it looked like the crab was going after him last night. this morning I can't find the urchin, but did see about 10 spine clippings in the sand were the hermit crab was. Are crabs natural <Many are> Is it possible that the crab killed the urchin, or is it more likely the urchin is hiding? <You can look about...> should I remove the crab? (the crab is ill tempered, eats all the snails and what not). Thanks for all the help, Justin <If you intend to have such animals... Bob Fenner>

Re: Urchin Howdy folks Do you consider the Mespilia globulus AKA blue tuxedo urchin "reef safe"?? <Some of us here do. Please see the coverage of this species on WetWebMedia.com Bob Fenner> Thanks again Joe Grunstad

Question on pencil urchin is it possible that my pencil urchin will eat my mushrooms and brown button polyps?<Yes> I read that they will but I don't know if its true? thanks JM <Cody>

Urchin blowing chunks! I have had my long spine urchin for some time now. I soon realized after buying that what I thought was his eye was the anal sack. <Such pretty bum, no?> He has almost doubled in size now and is very interesting to watch when he's moving about. <They grow very fast when they're little. I just recently removed mine because he grazed a path across a Montipora. Make sure it gets enough algae food!> Today however, he started spewing out this white material all around his sides while still moving all over my rocks. What is this white material? <Not sure, could be regurgitating stuff out of its mouth if it ate something it shouldn't have. Doesn't sound like something to worry about.> Is it a defense mechanism? <As far as I know, no.> Should I be worried? <No, just watch him for now. -Kevin> thanks, ART KOUNS

Reef Safe Urchins? I have heard rumors saying that all sea urchins are NOT reef safe until I found out about the pin cushion urchin which is supposedly reef safe. I had 3, local to Florida, urchins in my 10 gallon reef. They didn't do much damage to my reef, that I saw. What species are or are not reef safe? From what I understand they are algae eaters. Is it true ? >> "Beware of generalizations, as always". I guess I should be saying... Most urchin species from near shore, shallow environs are macrophagous herbivores (they eat algae you can see), but there are more generalized feeders, and many that can, will do damage to other sedentary or attached captive marine life via pincushioning them with their spines. For my part, I'd avoid the larger specimens of the larger species, just on the basis of size, possible physical damage they might do, need for space to scoot around and food requirements. Naming them? This would take some time... please see the survey piece on Echinoids (urchins) and their phylum (Echinodermata, the spiny skinned animals) at wetwebmedia.com for the basics on their selection, care. There are better "picker uppers" for most reefs. Bob Fenner

Urchins Dear Bob: I recently went to Bird World in Salt Lake City, UT and found an urchin that they called a decorator urchin. I was wondering if the blue stripe tuxedo urchin is a decorator urchin. The reason I ask is because I am interested in putting a couple in my reef tank and Bird World's decorator urchin look similar to the tuxedo urchin except different colors....it was hard to tell with all the algae and stuff on them but I think they where red colored. Also I was wondering if you could give me a list of urchins that are reef safe? Thanks, Boyd Bunk >> There are no absolutely reef safe urchin species IMO... too much chance of mysterious death-poisoning of the system, poking soft bodied tankmates.... And don't know the species that you're describing above... sorry... maybe a search on the Net under the keyword Urchin, Echinoids... could find you a picture of what you're looking for. Bob Fenner

Long tentacle anemone VS. small urchin Can these get along with small urchins? I've had both in a 55 gallon for a number of months, but the anemone keeps moving around and I think the 3 small urchins are stinging-bothering it. The anemone has started to get brown/dirty looking at its ends. <Hmm, you may be right here... any way to move the anemone to a "corral" of rock the urchins can't get around? Or maybe a steep-sided plastic or glass dish/bowl the anemone can reside on a rock/gravel in on its own in the system? Some way to exclude the urchins?> Wondering if a few months of mixing them has suddenly shown some incompatibility here. Everything else doing well. Have a few Condylactis anemones which also show the same brown trait, (more limited) but otherwise, are doing ok. One purple Condylactis shows no symptoms at all. I'm using the urchins for rock cleaning which they do very, very well. No other corals or fish are exhibiting any difficulties. Use your site often and enjoy the reading. <Thank you... Would try the above, otherwise not over-worry. The sort of brownish marking you describe I have seen in the wild time and again. Bob Fenner>

Long Spined Urchins -good or bad? Thanks for your input. I have another question for you... I am still curing my LR and have several organisms that apparently came with the rock. Included are 4 long-spined urchins (at least that is what they look like) that hitch-hiked in with my aquacultured Florida rock. They are now about 1 inch in diameter (from spine tip to spine tip). They have more than doubled in size in the 6 weeks I have been curing the rock and appear to be thriving. Would I be wise to remove them from the tank? Or will they be nice enough as long as I don't touch them? I would really like to keep them, but if they will be more trouble than they are worth, I suppose I should find a new home for them before they grow too large. <I would leave them for now... perhaps they will get too big, prickly ultimately... maybe not.> As always, thanks for your help, Jason <You're welcome my friend. Bob Fenner>

Sea urchins I have a 45 g. salt water tank. With live rock shipment (50 lbs) I noticed small sea urchins (black) they have doubled on the way to tripling in size in the last 7 weeks I now have between 9 -12 and only originally saw 4. My question is what is the effect on the tank having this many large urchins? They seem to spend a lot of time on the glass. Do I need to reduce the number of them will they continue to multiply and also to grow larger? Thanks for your time. <Good question... and "only time can/will tell"... I would leave them be for now, and count on their limiting themselves growth-wise, ahead of the practical possibility of over-grazing your system. Bob Fenner>

Triggerfish and sea urchins I have a black sea urchin about the size of a tennis ball or just a little smaller and I'm getting a 2.5-4" clown trigger and I know that triggers love sea urchins, so, is there any chance that the triggers wouldn't eat the urchin? <Yes... at the acquired size it is likely unfamiliar with urchins as foods. As long as this specimen is otherwise well fed, it will likely leave yours alone> I do have an extra tank to put the urchin into so I'm not just going to let the triggers eat the urchin (I'll move it out immediately if you say so). Thanks for your help! Kevin Ballard <Whichever system is more stable, has more rock, material to live on, I would leave/move the urchin to. Bob Fenner>

Live Rock question Hi, it's the pest again, <no trouble at all!> No way! Really? An urchin? Better get my flashlight out! <just a candidate... you have an uncommon situation... I can't think of a common occurrence to otherwise explain it.> If there is an urchin in there, will it hurt the Gramma? <certainly not> Also, what should I do about it if it's in there? <typically no... but if he is that destructive to change the rockwork in weeks to months, I'd say remove him> What do you think happened to the worm? Could it still be alive in there? <remarkably hardy... don't give up yet. give it a few weeks> I have discovered two new snails, (at least that's what I think they are) they look exactly like snails, about a half inch long now, but without the shell. It looks like they're growing shells now but are still soft. They clean the glass just like the other snails. <Yes, most likely a Stomatella species... reference a picture. AKA the paper shell snail... very fast moving, right?> Yesterday, I saw them do the weirdest thing...they were both standing UPRIGHT at the top of the rock and spasmodically spewing tiny white specks into the water above them. The two fish thought this was grand, and chased them around to eat them. I assume they were eggs. You think? :-) <agreed and wonderful!> Sorry to keep peppering you with questions, hope you don't mind. The big hole in the rock expanded over a period of about 4 months. Thanks again. Donna <my pleasure, Anthony>

Sea urchins with LPS? <Anthony Calfo in your service while Bob tours the Land Down Under... , "where women sew and men chunder."> I recently ordered a long spined sea urchin. What sort of threat does he represent to corals (I have yellow polyps, star polyps, mushroom and frogspawn corals, and hope to add brains and bubble)? <I'm thinking you might have wanted to ask that question before you ordered the animal <wink>. I have some good news and some bad news. First, the good-a news: I am one of the most sympathetic aquarists to keeping urchins in reef aquaria. They are generally efficient and inexpensive (in terms of bang for your buck) scavengers/grazers. They rarely id ever eat corals/invertebrates and the long-spine in particular is quite nimble for an urchin. OK... now the bad-da news: long spine urchins more than any other urchin are the worst in community with LPS corals as you wish to have. The mix is nearly irresponsible. While the urchin will not graze the LPS, the long spines can easily puncture the pillow tissue and knock skeletons over which can cause fatal damage to LPS (especially repeatedly). An awful mix. Do be sure to research an animal before you buy it, my friend. We have limited reef resources and they are living creatures. The long-spine Diadema make great scavengers in FOWLR display denizens. I had one grow to a size too big to fit into a five gallon bucket in a 300 gallon tank with a single eel for a tank mate. Magnificent and fascinating creature. Best of luck to you. Anthony>

Trouble with Tribbles Anthony, First let me start by reporting the best reef conditions I have ever had. Thanks to you and yours, water is better, skimmer is functioning properly, rock and inverts are thriving, and the reef is reefier! (Did I just coin a word?) <sounds delicious!> You guys ought to wear capes! <I used to wear one... but apparently it is unlawful to do so without wearing any other garment of clothing while standing in a park fountain> Yes, reefier. Has a nice ring to it. I'll be using that one again.) <just ducky! <winky>> I was scraping algae off the glass this morning for the first time in a couple of weeks, (snails are apparently getting lazy) and I noticed what looked like very tiny white bugs scampering around in the algae. Then I noticed that there were none left on any place I had scraped, and only collecting on spots I had missed. Upon closer examination, I could almost make out a tadpole (sperm) shape, they were white and definitely moving of there own free will. <perhaps you've discovered the secret ingredient in some of the vital/snake oil reef supplements?> I stopped scraping to avoid possibly wiping out a colony of something cool. Any idea what they might be? <well... many desirable microorganisms...amphipods, copepods and the like. Do look up some of Shimek's or Moe's drawings/photos of such critters. Very desirable though I'm sure> Also, a couple of weeks ago, against my better judgment, I bought a really cool long spined urchin. I took the advice of a reef store that said........"Sure he'll eat your precious coralline algae, but upon doing so, they expel the spores thus repopulating/propagating the species." Is this BS? <Hahahahahahhhahhahhahhahhahahhhahhah...........> <Ha... ha....he....hehe...he....hahahahahahahhahhahhahahhahhaahah> <woooo...hooooo...ha...hooo. Ahe...heheh. Ahem....> <Pat,...I do not believe that explanation by your LFS was entirely correct <tear>> I have noticed a whole lot of chewing going on. Can this little monster actually chew down my reef? or is the new coralline growth I'm starting to see (on the snails of all places) evidence of this. I hand picked all 75lbs ( and counting) of my rock for it's abundant coralline/calcareous growth and I'd hate to see it all devoured by this aquatic Tribbles, as cool as he is. <in fact, I agree that the long-spine urchin is pretty cool. Yes they can eat some coralline algae...but no, they do not shoot "Magic" coralline algae spores out of their bungholes....hahahahahahahah...heheheheh, wooohooooo. Oh, yeah! I got to get the name of that sales clerk and thank him for that one <smile>! Anyway... my take on the urchin/live rock deal is that I would recommend them for tanks that for whatever reason grow enough microalgae for them to graze. In such cases their presence serves the greater good. Else, they eat more coralline algae than most people can grow. If you see that exposed white carbonate material on the rock than pink, etc corallines sprouting...pull the urchin. Else, enjoy it>> Hey anyway, have 65 nice days in a row. If they ever come out with a small porous statue of you, I will surely sink it in the tank so as it seeds, my animals can all have someone to worship. <I'm actually hoping they manufacture my likeness in one of those springy tassel dolls that you can mount on the dashboard of your car. But if you do submerge a statue of me in the tank, please cultivate some long hair algae on my head so that I look taller> As always, thank you. -Pat <with kind regards, Anthony>

Pincushion Sea Urchin <<Greetings, Kim, JasonC here...>> I was given what I now know is a pincushion star as a gift for my smaller 30 gal aquarium. (After reading your site I know this is too small) <<Enough said, then... >> He is brown and stop sign shaped I offered him a silver side last night which he seemed to eat but this morning he was on top of my anemone devouring what was left of it which wasn't much by the time I found it. Since I do keep anemones in this tank I was wondering if he could be kept in one of my other tanks with a porcupine puffer, small lion, and snowflake eel or if he would eat them too or get eaten himself. <<Most likely that the puffer would sample it to death and much less likely that it would chow on any of those fish. Cheers, J -- >>

Re: Something is Eating Coralline By far, the most awesome gods, you are right! I have a pincushion and a pencil urchin. That's what is eating the coralline. poor giant emerald crab, I caught him and threw him into another tank. I guess I could put him back now...urchins...ugh. <<while I appreciate the kind words, I can assure you, I am quite human and make many more mistakes than any god should. But where were we?? Urchins... yes... they are like self-propelled Brillo-pads.>> yes, I supplement calcium and drip Kalk at night and etc, etc. little coralline dots growing everywhere else. <<Ahh good, well we've now solved the mystery of the missing coralline so no worries about the calcium.>> which urchin to remove or both? <<Well, depends just how much of the coralline they are removing - if you can live with a little loss - recall this is food for them - then keep them. I'm sure you can find balance there somewhere.>> can I put him/them into a tank with a giant carpet and two clowns? <<sure.>> another subject...cuz gods can do more than one thing at a time. <<well, actually, I'm done with that previous thing so... sorry to disappoint, but... one thing at a time here ;-) >> how do the fish retain color. I buy clowns from ORA and they are BRILLIANT. then they gradually turn regular color. what do they feed them. <<A better question to ask would be, what do you feed them?>> I am truly blessed to have such bright and attentive gods to watch over me.\reneeRN <<Cheers, J -- >>

Is an Urchin a Good Idea? The wife wants to add an urchin to our established (over 2 years) 180 FO tank. The tank has plenty of green algae and currently has the following: Harlequin tusk, Niger trigger, Arc-eye hawk, Bi-color parrot, Koran angel, 3 scissor-tail gobies, Pearl goby, Banana wrasse, African red star, Green brittle star. I've read the information on your website regarding urchins and I'm worried. What problems can I expect? <The most they can do is eat desirable algae and knock over stuff.> The information indicates that it will eat "everything"... does this include fish or just algae/coral? <No concern for your fish to get eaten with most in the trade. For the most part, they eat algae, some will eat Corallimorphs, and many will knock corals off their perch.> What about waste/ammonia, which was indicated as being a possible problem? <No worries.> The tank is kept at 80 degrees, w/UV sterilizer, 1/2HP chiller, protein skimmer.

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