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>

Sea slug Toxin? Oh yes  02-05-06
Morning guys!
<Too cheerful...!>
Just found your web sight and it's now booked marked!
<And the site too?>
I've been searching all over the web trying to find an answer to my problem! About a month ago I purchased a beautiful sea slug. A week later I found it dead, caught in my filter.
<Yikes... am trying to put away the pix from the last trip... and am on to the Opisthobranchs... and reading re just how toxic some of them are... no wonder they can be so gorgeously colored and not predated, eh?>
A week later all my fish except for one damsel were dead! ( Niger Trigger, reef beauty, butterflyfish, cardinal, yellow tang) I forgot to mention that my tank is a combo reef/fish 50 gallon. My soft coals and one Anemone were not affected nor were the cleaner shrimp, hermit crabs and turbo-snails. I immediately suspected the death of the sea slug and sure enough read that these slugs secret a defensive toxin.
<Yes... but not so much a secret to the fishes they're found with... just in the confines of an aquarium...>
I performed a 50% water change and replaced all my filters. I let the tank "stand" for 3 weeks then introduced one blenny to the tank. Within 36 hours it died! It's skin was sloughing off and fins looked as if they were dissolving.
<Yep>
My question is; should I completely start over with new live sand and live rock??? ( the rock is still very purple in color) or let the tank recycle for a longer period of time???? HELP!
Great sight,
Jim
<Mmm, if it were me, mine I'd try adding a good quantity, quality of activated carbon in your filter flow path, let another few weeks go by and try some other "test fishes". Bob Fenner>

Sudden Fish Loss, BGA wipe-out 7/18/05
Yesterday I experienced sudden fish loss which freaked me out. My system has been up and running for 3 years with no major problems.
46 Gallon
About 70 pounds live rock
5-6 inch fine sand bed
AquaC HOT skimmer
Magnum 350 canister (for Carbon and Mech. filt.)
A couple power heads
Medusa Temp controller (hooked to small fan and heater)
Ground probe
Live stock:
Regal Tang (I know, too small a tank but didn't do my homework when I first bought him)
2 Ocellaris Clowns
1 Chromis
Coral:
Bubble, Candy Cane
Yellow polyps, and a few mushrooms.
4 Turbo Snails
Have not done any tests in a while, SG 1.026
I am currently going through a Cyano out break and got lazy the past week or so and let it build up on the glass. I used the Magnet and cleaned off most of it from the glass, of course there was a ton of it floating around the tank so I reached my hand in and took the screen off the canister filter intake so it doesn't get clogged and it can suck up the floating blue-green algae. About a half hour later I glanced at the tank and noticed the Chromis was dead and the other 3 fish were gasping like crazy. The clownfish were on the bottom gasping and having trouble staying upright, the tang was gasping also but seemed to be handling a bit better (I guess because he is a lot bigger), The starfish then ate the dead Chromis. I had no reserve saltwater so I hurried and mixed a batch of fresh saltwater, (obviously you are supposed to let it mix for a couple days in normal situations) the salinity was a bit off cause it was the last of it (about 1.023), I put the worst of the clownfish in there but he didn't last long and died. I then put a fresh batch of Carbon in the canister filter
<Which I hope/trust you rinsed of the Cyano>
and let the remaining 2 fish stay in the  tank.
<No... move them from the toxified water>
The 2nd small clownfish died overnight I think. I believe the starfish ate him too because the central disk was a big bulge this
morning . The Regal Tang seems kind of OK, it looks pretty lethargic but I put a few flakes in this morning and it did eat. Also he is not gasping like crazy anymore.
The coral and polyps seem to be ok, they extended there tentacles last night to go into feeding mode. The starfish is fine I assume, especially since  it ate 2 fish.
I did do an ammonia test this morning and results showed no ammonia (old Salifert test kit though not sure how accurate it is anymore). So could have the tons of Cyano
floating around have caused the sudden fish loss?
<Oh yes>
I don't think it was me putting my arm in the water, I don't recall handling any chemicals or anything that would be toxic. I am at a total loss here. There is also a couple Caulerpa (I believe) stalks growing not sure if that could be hazardous in any way. I do have a small toadstool mushroom that is being taken over by blue green algae, could it have released some kind of poison?
<Possibly>
The system has been running just fine for 3 years and all of a sudden this happens and
I have no idea why. Its kind of discouraging, I wanted to replace with a bigger tank at some point
<Much more forgiving...>
but am now re-thinking that idea. So any ideas?
Thanks.
Angelo
<The BGA is likely the primary culprit here... need to be diligent about keeping it steadily kept down... A larger system, with a sump/refugium will be much more stable, easier to maintain. Bob Fenner>

Cowfish Poisoned Tank
Hi Bob,
<George>
   I have a 120 gallon tank I converted to salt water about 4 months ago and went through the cycle and all my fish were doing fine. About every other day I checked the salinity, nitrite, nitrate, pH and ammonia and they are always perfect.  I had 2 Yellow Tangs and A Powder Blue Tang
<Not easily kept>
and a few Damsels and about 2 weeks ago I purchased a cowfish. The aquarium store I purchased it at didn't tell me the fish was poisonous and if they had, I wouldn't have bought it.
<This is mentioned several times, places on our site: http://www.wetwebmedia.com/boxfishes.htm>
It seemed to be OK for a day or two and then it kinda started just floating around in the tank, swimming a little every now and then. I told the pet store I purchased it at and they said that it was just stressed because it was in a new tank and that it would be OK in a few days. I believed him and then the next afternoon when I came home from work it was hung behind one of the decorations I have in my tank and it was dead.
I carried it back to them and they gave me a different fish to replace it.
When I got back home about 3 of my other fish were dead and the others were swimming around with hardly no life at all. Then, the  next afternoon they all were dead. I found out that if the cowfish becomes stressed before it dies it releases a poison that will kill everything in the tank and it did.
I went to a "Barnes @ Noble" book store and after looking through all their Aquarium Fish books and reading about the cowfish they all said that it was poisonous and it will release a poison if it becomes stressed and it will die instantly and poison the entire tank, and  it did. Over the past two weeks since this happened I have changed about 50% of the water 3 times and one time I changed about 75% and each time I did a test on the water and it was all perfect.
<I would change ALL the water... in fact, if this were an account, I would drain it all, re-fill it with fresh and lightly bleach (acid) wash all... yes, killing all biota, oxidizing the ostracitoxin>
I have also replaced the  carbon in my two filters every other day as I was advised by the aquarium store. I have added a few damsels to it and they have all died after being in the tank after about 2 days. Every time they died I purchased 3 more damsels and about 2 days later they died. They all seemed to be doing well and then the next morning when I turned the lights on they were all dead. I am trying everything I can think of. I would appreciate any suggestions you have before I recycle my tank.
George
<Sorry to hear of the losses here. Please refer to WetWebMedia.com re how to thoroughly clean your system... and start over from "square one". Bob Fenner>

Sea apples -Nooooooooooooooooooooo!!!!!!!!!!!!!! - 11/24/03
Hello I believe I have a Australian Sea Apple, and the other day it was secreting yellow little balls, possibly eggs. <Possible...either way....not good!!!>  But the next day 2 of my fish died. <Craaaaaap. Sorry to hear about that. Yes, well, this is why these are not good in mixed aquaria. Either dedicated tanks or not at all my friend.>  I was curious if it was from eating those balls. <Absolutely, but just being in the tank with this noxious material would be enough to kill everything in the tank! Doesn't even take eating it. Do read about this on our site.> I did a 90% water change <More frequent water changes with about 30-50% daily might help. 90% percent was probably necessary though. Do read up before purchasing any inhabitant you are to take into your charge. Good luck ~Paul>
 

- Sudden Fish Losses - Bob, <Actually, JasonC here this morning...> I must say, your writings have been a Bible for my husband and I when it comes to our 185 gallon reef tank. I wanted to ask you a question as we value your opinion.  Over the last 3 weeks we've lost a massive amount of fish.  Our water conditions are Perfect!  We do our water changes, test the chemicals etc... our tank is well established and has been up and running for about 6 months. We noticed some symptoms of what we believed to be Ich.  The fish had white patches (some had small white spots), were flicking themselves on rocks (scratching), BUGGING our cleaner shrimp way more than normal and they would completely lose their appetite.  Once we noticed the symptoms, we would remove the fish from the tank and freshwater dip them.  We would also put them in our quarantine tank (a 55 gallon) with medication if necessary.  We were using the Mardel-Two.  A few died in the medicine tank, I am assuming because of the stress of moving them (two tangs and a blue Angel).  Slowly though, all of our fish died:  Emperor Angel, Coral Beauty, 2 Clown Fish, 2 Zebra Damsels, a Hippo Tang, a Brown Tang, a Black Velvet Angel, a Lemon Peel Angel (of which we still have not found the bodies of the Black Velvet or the Lemon Peel).  The only survivors were 3 Blue Damsels. Now though, we are getting VERY worried as it is happening really fast with the NEW fish we just got!  I know that when you move fish from your quarantine tank to the "Final" tank that it will cause stress and could cause fish to possibly die (although we are extremely careful). <Uhh... I don't agree with that. The fish have already been through their original capture and transport which is very stressful. Transfer from quarantine to the main tank might be stressful but not nearly as much as some other things - like overcrowding.> But, we are seeing fish healthy, happy, eating, not scratching.... dying within a few hours!  Just tonight, I fed the fish and our Blue Spotted Angel, came out and ate.  Just 15 min.s. ago, I saw him being pushed around the tank in the current, then falling to the bottom, barely breathing.  I immediately removed him, put him in a 5 gallon bucket with an air pump and covered the bucket with a clothe to make sure he wasn't disturbed by any light.  When I put him in, he flipped out, tried jumping out of the bucket a couple of times (scared the death out of me because I don't know where the "spurt" of energy came from). He died a few minutes later. <It sounds to me like some contaminant has gotten into your tank - perhaps a household cleaner... does anyone in your house smoke cigarettes? Or as another example of cross contamination, if you put flea and tick medication on your dog, then scratch/pet the dog and then place your hands in the tank... bad news. Please read here: http://www.wetwebmedia.com/toxictk.htm > We have a Tube anemone that yesterday was trying to eat a Yellow Striped Maroon Clown.  The fish was dead but he had about 1/2 of him in his tube.  This worried us because, we don't know if the Tube Anemone maybe stinging our fish and maybe this is a cause of the deaths.  We have other corals.  We have a Frogspawn (2 of them), a Torch, an Elegance, Xenia and a yellow polyp.  They are all doing great, fully expanding etc.... <As backwards as it might seem, many invertebrates are actually more tolerant to environmental pollution than are fish - mostly because they can't move, they've developed a tolerance, whereas fish who can usually 'run away' in this circumstance cannot, so... you need to look for things around your house that may have got this problem started.> Again, we just don't know what is going on or what we should do! <I'd start by running activated carbon inline with your filter system.> Have you ever heard of a Tube Anemone doing something like this? <Sure.> Or do you think our tank is diseased?  Either way, what would you suggest doing? <Some large water changes along with careful investigations as to the source of the problem. Do you have a protein skimmer on this tank? Has the skimmate changed or is there more 'stuff' coming out of it?> Thank you so much for your time.  We have consulted all of our books etc... and we have tried the freshwater baths, the medicines, we practice quarantine our new fish etc.... and we just have no idea what is going on or what to do. I am so worried about the fish that we have in there now. Again, thank you for your time, Danielle <Cheers, J -- > - Sudden Fish Losses, Follow-up - Thank you very much for your response! <My pleasure.> Our skimmer isn't producing more than they normal amount of waste but, obviously that doesn't mean that it is not contaminated.  We are going to do our water changes and put some fresh carbon etc... to clean this things up.  We have the Protein Skimmer and an External Filter.  We are going to do the water change in just an hour or so. Do you think that the fish we have in there now should be removed and placed into our other tank? <I'd actually hold off... as long as they aren't expensive fish, I'd leave them in there for the canary in the coal mine factor, if you know what I mean.> Also, with the Tube Anemone, fish obviously swim by him and I am assuming that maybe that's when they are getting stung. <Most likely at night, when they can't see the anemone so well... you would think they would know better.> Can you tell me what the signs/symptoms are when a fish gets stung by a Tube Anemone? <Outright death... have not ever seen a fish survive this.> Again, thank you so much for your help! <Cheers, J -- >

Plankton outbreak Hi Bob, I have a 75 gallon reef, I just have a problem I hope you can help with. A week and a half ago, a pet store gave me a sample of DT's Phytoplankton to try, the dosage on the bottle is 2 cups per 100 gallons, they gave me a cup, I put it in my tank and it turned green and boy do I mean green, now I can't get it out it keeps blooming. If I turn out the lights it get a little better, but I can't leave the lights out for long as I am afraid it will kill my corals ( which are doing fine). I have VHO lighting, filtration is a Fluval 300, 3 power heads, a skimmer, and a hang on the back filter loaded with carbon ( which was suggested that I do to pull it out ( no luck) Now it is suggested that I put on a U.V sterilizer, but won't that take out all the elements that I have put in? Can you help? JoAnn >> Think so... I would install a pad of PolyFilter at this point... that will slowly remove some of the necessary nutrients for the phytoplankton, and your system will clear in a couple of weeks. The UV would work as well, but the sudden release of materials bound up in the algae will cause other problems for you...  Bob Fenner Plankton outbreak Hi Bob, Thanks for the reply, My corals are starting to suffer from insufficient light if it takes a couple of weeks, do I risk losing my corals? This stuff is thick I think the light can't get through. JoAnn >> Hmm, in that case, do ask the store if they'll lend you a "diatom filter" (Vortex Innerspace Products)... have them charge it with media, and show you how to set it up and run it... or if they have a "skid unit" with a few micron mesh cartridge system that they can run for an hour or two... Either of these will filter out most of the single cells for now... Otherwise, the low light condition should not kill your corals. Bob Fenner

Question "help", shipping water?
My question is: I set up my 55 gallon tank about 10 weeks ago and have added about 70 lbs total of live rock. I currently have a leather coral, and 3 sea anemones. When I fist started my tank I added about 7 damsels, and since have taken them back to the pet store and added different fish clowns, Banggai Cardinals). After several days of adding the new fish they died. I went to the pet store and they recommended I treat the tank with Tetracycline to see if that would help. I treated the tank, did a 50% water change. and after a week I added 2 Percula Clowns and they died 3 days later. I have checked the ammonia and nitrates, they are both 0. Some of the fish, before dying, hover at the bottom and look as if they are gasping for air. Others look liked their skin was being peeled off a little at a time (No white dots, but looks like they have been scraping themselves on the rocks. I added an airstone to the tank before they died thinking maybe they did not have enough oxygen, but they still died. Currently, I have a 50/50 bulb, an actinic bulb, a protein skimmer, a power head, and an Emperor 400 to filter the water. 
Do you have any suggestions as to why the fish continue to die, and maybe any suggestions as to what I can do? I am not sure what to try next to see what  is going on.
Thank you very much. 
>>
Thank you for writing... Did you happen to pour any of the shipping water into your tank? This situation sounds like one or more of your anemones has "shed" enough (cnidocytic) material in the water to render the observations you're relating... There are a few things I would do at this point. If you can mix up enough synthetic seawater, a massive (80% or so) water change. And the addition of a Polyfilter pad to your filter flow path... and take all your filter material out and thoroughly wash it in hot, freshwater... thoroughly wipe down the inside aquarium panels (glass or acrylic) then wait a good month, and "try" another "tester" damsel...
Bob Fenner

Tank death
Hey there,
It's me again. Remember the Tang. He past away the day I talked to you about feeding him. Yesterday I lost the rest of the fish in the Tank. No Illness signs at all. My main tank and the secondary tank in unaffected with this problem. I check the water and everything is fine, except the ammonia way in the low-mid level range. Could it be reef disease??? If so what can I do to clean the tank???
<Hmm, disconcerting... and I don't remember much about my emails... many going through every day... But anomalous losses are a source of concern/worry to me... Generally attributable to a "hobbyist" poisoning input... like errant metal contamination, spray cleaners in the room, mis-use of "additives.... or an internal job of algae, sea cucumbers... some combination of interactions... But, other than idle speculation, what can be done at this point? Typically, near total break downs to massive water changes and use of chemical filtrants (carbon, resins), followed by slow addition of "test" organisms to re-stocking...>
The last question, in my main tank I have 5 kinds of mushrooms. All died except the hairy Tongo. What could cause their deaths. When I notice a signs of coral problem I change 5 gallons of water from the tank with 2 day old RO sea water. I also lost the green star polyps also. My collection of Xenia is doing fine. I will be doing a partial water change again tonight. I'm also running carbon to help filter out poisons that may be present. Any Suggestions?? Water quality is fine except Ammonia slightly present in the water. Only have a Mandarin goby and a Clark Basslet.
<Oh, here come the clues... yes to the biological chemical warfare possibility alluded to above... The winner(s) are usually the better part of the cause(s) of these sorts of wipe-outs.... And sort of like re-doing your computer's main drive... start with these "winners" and add more software/livestock that are compatible with them... You shouldn' t have any ammonia... this is a residual of the die/kill off and ongoing skirmishes... Wait till it's all gone, develop a stringently regular water changing, chemical filtrant use program (monthly)... and a careful re-stocking plan>
Thanks, Anthony

Thermal Shock... downward
Hi, I'm working to the Quebec aquarium, and one of my lionfish got a thermal shock last week. The temperature normally at 25 degree Celsius, fell to 18, and the fish turn over. Is not dead, but he look bad on his back. He don't eat anymore. Can you help me to help the beautiful fish?
Thank you for your help!!!
Geneviève Poulin
>>
With luck this specimen will recover... even if it doesn't eat for a few weeks (not a typo). Try to keep its environment stable, and be patient.... I know of worse cases that have turned out okay.
Bob Fenner

A real mess... thermal stress plus?
Dear Bob,
I'm mailing you from Adelaide, Australia with a nasty dilemma.
I have a 5ft marine tank containing 12 fish from damsels to clowns to a golden headed sleeper, approximately 20kg live rock, an anemone and a painted crayfish. I've noticed over the last few weeks large white/light brown growths on some of the fishes faces. My local fish shop suggested it was white spot and so I've been using MYAZIN once a day, which is supposed to be OK for the anemone and Cray. I've also increased the temperature to ~29degrees C and the salinity is low. However, the fish show no change. I've lost a tang and bicolour angle, both I found on their sides gasping. Some of the other fish are now doing a lot of scratching. I've recently moved (three weeks ago) and in the process managed to crack the tank which has made my trickle filter inoperable, so I've been relying on an undergravel filter and an internal powerhead with some filter media attached.
Help?
Patrick Sim 
>>
Yikes, a whole lot going on here! Can you characterize these markings on your fishes faces? I suspect this is really not a parasitic infestation at all, but likely a stress reaction from... the high temperature... and??? What I would do is stop with the treatments (likely related to your losses... and the scratching behavior) and look into ways to lower the temperature of the system, get that crack fixed... Maybe leaving the lights off by day... perhaps rigging up a fan to blow air across the top during the day... maybe even floating a frozen plastic jug of water in the system on the hottest of days...
But, let's get the remaining life into another system so you can effect the repair (maybe just siliconing a bit of thin acrylic sheet over the cracked area...) and the wet-dry sump up and going. Bob Fenner

Sick Tank, Animals, or both?
I have a 55 gallon tank with about 20lbs of live rock in it. The tank is two weeks old, but I 've had the live rock for a week. Problems arose as I noticed that two of my four striped damsels were suffering from scale loss and fin decay (I noticed little white particles on their fins). To tell you the honest truth I really could care less about the damsels. I moved them to a 15 gal tank along with my ten hermit crabs (after freshwater bath). I pretty much narrowed the cause down to a bacterial infection of c. columnaris, streptococcus, or Vibrio. I ordered some Ampicillin and will begin treatment when I get it. my question is (finally) suppose that my diagnosis is correct and I cure my fish. the 15 gal tank is clean of infection but what about the 55 gal tank? there's nothing but live rock in there and I plan on adding medication to the tank anyways to prevent a second infection. will the medication kill the 'good' bacteria in there?
<Probably the new tank was the real cause... and I would just let the 55 "go fallow" for a month... and not worry otherwise>
what about the live rock, will it 'buffer' some of the 'bad' bacteria and protect it from medication (absorbed into the pores)? your help would be nice but its not an emergency. by the way your site rocks, I appreciate your unbiased opinions on all subjects.
<No worries my friend. Go ahead with your livestocking plan in about a month. Bob Fenner>

Depressing start, please help.
Hello,
I recently bought a 92 gallon corner tank with a bio filter, protein skimmer, and canister filter.
It was stocked with 88 lbs of live rock, and three days later I added 6 fish to begin the cycle.
3 green Chromis and 3 of the NOT TRUE Percula clowns.
<Yikes... should have waited...>
3 days after that a clown has just died, and for about 2 hours went all around the tank upside down and banging into things. He seemed to be fine the first couple days, although none of the clowns like to come out of hiding, even when feeding.
The green Chromis are quite energetic though.
<Stress, and all induced...>
Please let me know if that death was "normal" or have I selected incompatible specimens. I hope to avoid any ignorant mistakes in the future.
<Very normal... Patience my new friend...>
PS: Live rock seems to have so many problems... anemones, worms, etc
Why don't people start out with sterile rock and build it up without the pests?
<Good idea... we have a few thousand pounds that we do just this for... and "cycle it out" for new about every six months...>
THANKS, Michael
<Do read over the set-up sections posted on the www.wetwebmedia.com site and give your system a month or two holiday from stocking for now. Bob Fenner>

Carnivores won't eat 8/5/05
Hello gang,
  I've a 125 gal marine tank, with 50-70lbs of live rock, currently housing, amongst others, a Dendrochirus zebra, and a Diodon holocanthus.  Not quite 2 weeks ago, the lion stopped eating, and the porcupine followed 3 days ago.
<Bad sign...>
  Both had previously fed with considerable gusto on krill, ghost shrimp, pellets, and the odd bit of chopped table shrimp.
<Bad diet...>
Both fish attempt to eat, but either turn away as soon as they reach the food, or spit it out as soon as they get it in their mouths.  None of the other fish (lunar wrasse, 2 Fiji blue devils, 1 domino damsel, powder blue tang, Foxface lo, snowflake moray, ocellaris clown) exhibit this behavior, and usually rush in to take what the other two ignore.  Also, the lion's gills seem to be a bit puffy.  All water chemistry checks out ok, save a very high nitrate level I've been fighting with.
<Bingo... need to fix this>
  I've tried other foods (silversides, Mysid shrimp, crab, and squid) but have had no luck.  Anything you could suggest would be very helpful.
Thank you,
Jacob
<Fix their environment Jacob. Read here please: http://www.wetwebmedia.com/nitratesmar.htm
And the linked files above.
Bob Fenner>

Goin' On A Hunger Strike - 08/11/2005
I have a 150 gallon marine tank.  My dwarf lion (D. zebra) has not eaten in a month (frozen krill).  
<Disturbing....>
Have tried many ghost shrimp, crab, shrimp, etc. to no avail.  My 8" snowflake eel seemed to be having trouble eating also and recently died.  
<A major concern....>
He did not seem thin and actually seemed swollen.  
<An excellent clue....>
My 5" porcupine puffer quit eating for 3 days but now is eating fine. frozen krill).  My powder blue tang and other herbivores seem to be unaffected.  No change in appetite or behavior.  The lion appears to try to suck in the food but cannot.  My water quality seems good.  
<Seeming good is not enough info....  Be certain ammonia and nitrite are ZERO, pH 8.3, salinity 1.021-1.024....>
But my nitrates are high.  
<Also of concern.  How high?  Above 20ppm can be an issue.>
I have done additional water changes (more than normal), I run a UV sterilizer, protein skimmer and do regular filter changes.  
<Try to find the source of your nitrates....  I would be concerned that the tank may be overstocked if you cannot keep nitrate down with reasonable water changes.>
No fish in the tank have bad fins, color or any abnormalities.  And there have been no recent illnesses or fish additions.  I would appreciate any suggestions.
<My first guess is purely environmental issues.  Get more water changes done, pronto, if anything is mildly amiss there.  Try feeding foods soaked in garlic extract to stimulate an appetite.  If still unsuccessful, you might want to consider the possibility of internal parasites....  the swollen eel, after having not eaten, may be an indicator, here.  Are any of the fish excreting long, clear-ish strands of poo?  You might consider offering a food medicated with Metronidazole or Praziquantel, or treat these fish in a quarantine tank with either of those in the water.>
Thanks.
<Wishing you well,  -Sabrina>