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FAQs on the Hydrozoans 1

Related Articles: Hydrozoans, Cnidarians, Fire Corals, Stylasterines, Hydrozoan Jellies,

Related FAQs: Hydrozoans 2, Hydrozoan Identification, Hydrozoan ID 2, Hydrozoan Behavior, Hydrozoan Compatibility, Hydrozoan Selection, Hydrozoan Systems, Hydrozoan Feeding, Hydrozoan Disease, Hydrozoan Reproduction, Medusoids/Jellies (Ctenophores, some Hydrozoans, Scyphozoans): Jelly Identification, Jelly Behavior, Jelly Compatibility, Jelly Selection, Jelly Systems, Jelly Feeding, Jelly Disease, Jelly Reproduction, Fire Corals Lace Corals, Stinging-celled Animals

Aglaophenia cupressina in N. Sulawesi. 

Digitated Hydroids
Good afternoon crew, <Good day> I posed a question on the forums last week, and no one really had an answer for me. The only suggestion I got, was to email you all and see if you had any good info to share with me. Thank you for any assistance you may provide. Here is the original post from the Marine Invertebrate forum:  Here is the situation: I currently have 5 of these nasty hydroids (digitated hydroids). Two of them extend to 4in. at night, two of them extend to 3in., and one of them to about an 1 1/2 inches. Of these five, I can reach 3 of them (one large, one medium and the small sized one). The other two are nestled deep into the back of my largest live rock, and there is no way I can get to them. Even if I was able to move all other LR and creatures off of it, they are in deep crevices that are barely wide enough to stick a nail in. Here is my question (which you could probably guess.. hehe): Does anyone have good experience with removing these type of hydroids? If so, what was your method? Also, I have had different hydroids in the past, not many but a few, and they generally cycled out within a couple weeks to a month. If you have had them before (the digitated kind), how long did it take for them to cycle out? I wouldn't even mind letting them just do that, except a few of them are getting way to close to some of my corals at night, when they extend themselves. Current setup: 100g 30g sump/fuge (LV, 4in. LS, macro algae) AquaC EV180 12x turnover Magnum 350 canister (changed weekly with carbon) 100lb LV Test readings: NH3/NH4, NO2, NO3 = 0 pH = 8.3 Temp = 78 to 80 Ca = 400 ALK = 9 dKH SG = 1.024 Kent sea salt, 10 to 15% weekly water change, no additives <Erica, if it were me, I would get a syringe from the pharmacy and make up a strong solution of Kalkwasser and when the buggers are out, inject them with that. It should do the trick. James (Salty Dog)>
Many thanks and ID question... First, let me say "thank you" for myself and all the others you have helped.  I've been reading and absorbing as much as I can from your site. <Ah, good> Some LR added to my tank has apparently been "dead rock" for over a month; it was a very small piece, and I bought it because I had thoughts of adding some zoos to it later.  It has been slowly coming to life, and recently sprouted a small colony of about 20 little thingies.  They are very tiny (~2-3mm tall) and look like a small wind turbine -- narrow stalk and four 'arms' in a cross at the top with small dots at the ends. <I see them... Hydrozoans of some sort> I've attached a picture, hoping that you can ID them. My apologies for the focus, but even in macro mode, they are tough to capture. Thanks again and warm regards, Matthew <A good enough pic. These can be troublesome creatures as a group... stinging you and your livestock... but generally they "cycle out" of their own accord in time. Please read here: http://www.wetwebmedia.com/hydrozoans.htm and the linked files (in blue, above) where you lead yourself. Bob Fenner>

Digitate hydroids I have recently set up my first salt tank and purchased some live  rock.  I noticed that there was some strange come out of the live  rock.  I did an internet search and have found out I have at least two  Digitate Hydroids.  One completely disappears when the light comes on the  other is about a tenth of an inch long.  It is about three inches long with  the lights out the other is about an inch or two.  I have not been able to  find much information on these creatures.  I want to know if they are  safe. << Yes, I would keep them and not worry about them. >> I also need to get a moon light to see what I am missing. << A flashlight in the middle of the night comes in handy as well. >> Thanks, Ed <<  Blundell  >>

Stinging hydroids 6/15/04 Hi Guys <cheers> Wonder if you can help me. Are there any species of fish or invertebrate which would feed on stinging hydroids? I'm having difficulty controlling them in my tank. Thanks and regards Adrian <while there are many fishes and invertebrates that will control hydroids... they are not likely to safe with your other fishes and/or invertebrates (Cnidarian feeding Chaetodontids, Asteroid sea stars, etc.). And if you could ID your species of hydroid and find a Nudibranch, for example, that was an obligate predator... the Nudibranch would soon starve. Your real solution is to get to the root of the problem (excess nutrients) and not focus on the symptom (hydroids flaring). Focus on starving them into submission and then polishing them off with a lite bit of manual control. Improve water changes, be more aggressive about skimming, increase water flow to get excess food/particulates exported rather than lingering to feed the hydroids, etc. Best of luck! Anthony>

Threaded Hydroid? 6/12/04 No emergency here, just trying to better understand my tank. I have a nice, healthy Devils Hand (Lobophytum) that at night puts out one or two relatively long (up to 7 inches) thin fibers that have "off-shoots" about a quarter inch long spaced at regular intervals.  It looks like a tank sized long line fishing rig.   <yikes... this is not actually part of the leather coral, although it looks like it. I have a strong suspicion here. One of the threaded hydroids. Does this thing look like a barely discernable wisp of a thread... and the "branches" like teeth on a sparse/coarse comb?> The fibers come out of one of the yellow fingers.  Is it trying to feed or is it a defense mechanism.  If the latter, should I avoid placing another coral within its reach? <yes regardless... keep all other critters away. And if its a hydroid, watch your arm too... a nasty sting is possible> Many thanks.  Your site has made a material contribution to my 38 gallon reef's growing success. <no worries my friend... if this is a hydroid, it can be removed (and future ones can/should be screened by running all new livestock faithfully through a proper 4 week QT). Anthony>

Threaded Hydroid? II 6/12/04 Many thank you for the id Anthony.  I am not worthy of such expert advice. <we are all on equal footing here my friend... as aquarists we each have our specialties, and we all evolve in time> I only found one picture on the web that looks like it, the "sparse comb" you so aptly describe.  How shall I remove it? How about cutting off the finger it emerges from? <no need to cut the leather, just look at the base and see if you can see ho well it is anchored (often appearing like a transparent fleshy plate/base in the case of this type)> Will it move around the tank if I leave it?   <not too motile> After just 8 months with the reef, I am clearly in new territory here... Dan <its all a learning process... no worries. Enjoy the journey. Anthony> Unidentified Critters... stranded hydroids 6/9/04 I have had a 30 gal reef tank for about a month now.  I have 45 pounds of live rock and 3 corals so far.  Also some snails, hermit crabs, a sand star and a blood shrimp.  No fish yet. I have been diligently checking chemical balances and everything seems on target.  In the past few days I've noticed some unusual critters appearing on the glass and live rock.  I've seen several very small snails (1/32 inch) which began appearing before I introduced snails into the tank, so I assume they've come from the LR. <yes... indeed> In the past week I've noticed several translucent critters on the glass which move like snails, have no shells, are about 1/8 inch long and have 2 points at their back end. <sounds like a flatworm... the little milky white ones prey on copepods. All are harmless> From reviewing other questions responses you've given, I've identified them as flat worms which are not harmful.   <Ah, BINGO- you win the hairy kewpie doll! Very glad to hear you in the archives :) > However yesterday I've noticed a new critter which, in reviewing your Q&A's, I cannot identify.  These seem to have emerged within the past day.  They appear to be long white strands with a single row of "hair" (1/16-1/8 inches long) on one side. (Almost like a 1 sided long skinny white feather.)   <Yikes... I recognize it already. It is a very distinct description. Your creature is a fiercely stinging hydroid. Do remove it... it will sting you and your animals alike> They seem to be about 2-4 inches long and appear to emerge from a jelly like polyp on the rock. They drift with the current from my power-head, and periodically retract back into the polyp.  I assume that they are "netting" micro-organisms, then "reeling them in" to be consumed. These strands are so thin that they are not visible unless you are very close to the glass.  Any idea what these things are?  Are they dangerous to the other life in the tank? <yes... do be careful. Best of luck, Anthony>

Ref: invert ref guide-j. sprung.  Myrionema/stinging hydroid. I was quite pleased with them until I found out they are pests. now I feel like I was bragging about a tank full of anemones! Aahh, oh well. all blissful ignorance must come to an end at some time. <Embrace the change. Bob Fenner>

Brown pom poms: hydroid ID 3/17/04 please identify these brown pom pom like polyps that are growing on my LR with my yellow stars. They are spreading and having a hard time getting rid of them. <they are the nuisance hydroid Myrionema and they can be a serious problem> I have been trying to rub them off with my fingers and they come back quickly. <Yikes! touch nothing in the tank with bare hands/fingers my friend! We have seen/written about (see archives) folks get seriously injured/ill this way. Piscine tuberculosis, Vibrio infections, etc> Please tell me the best way to get rid of them. See attached photo. thanks Ron <use the genus name provided above to do a keyword search of our archives (Google tool at bottom of our homepage) and beyond on the internet. Best regards, Anthony>

Bad boyz- hydroids 12/30/03 Hi guys <howdy> Can you please identify these "creatures", they are about a quarter of an inch long and have a "coil" at their base. I'm also not sure about the green bubbles. Are either of these a problem? <the tube-like critters are stinging hydroids and the bubbles are a Valonia type algae or Halicystis stage of Derbesia hair algae. All are pests. Do read through our archives of articles and FAQs for the (nutrient) control of such organisms> Thanks and regards Adrian
<best of luck my friend. Anthony>

Unknown animal, invertebrate, probably hydroid About myself: for the past twenty-five years I have been a developer of advanced performance materials and only recently started to maintain marine tanks. I have always been fascinated by the marine environment but in the past mostly enjoyed it from a canoe (frequently at night) on the Chesapeake Bay and the Albemarle Sound. <interesting... and are you a member of the excellent local aquarium society, CMAS? Do look them up.. great club.> About my tank: the tank in question is a refugium that I could never bring myself to hook up its main tank. It was too fascinating to risk ruining. It is 20 g with Inland Aquatics detritivore and refugium flora kits 20lbs live sand and 10lbs live rock (one piece) 2x65W 6500K PC lights, no filter or skimmer - just a single airstone. After Hurricane Isabel, it went 6 days without any lights or aeration (we had no power). Only obvious loss of life was one very small snail. Upon return of power there was a slight cloudiness that immediately cleared and was followed by a slowly worsening algal storm that grew day by day until visibility was only a few centimeters. Much of my macroalgae died and my copepods began to disappear. At the same time a new animal began to appear in increasing numbers. Here is a snapshot of it: <a Cnidarian... looks like/is likely to be a hydroid IMO> It was about 1 cm in diameter and appeared to me to be some kind of hydroid larva. <agreed... not uncommon> The algal storm finally cleared and simultaneously the mystery larva disappeared. I now have thriving copepod swarms and a goodish bit of Cyanobacteria on the substrate. <increase water flow and protein skimming to eradicate this Cyano> My son and I have looked hopefully for some polyps to appear. We are quite excited by the prospect of finding the adult animal. But so far we have not seen anything new. My question: What is the mystery larva? Where did it come from? Where has it gone? <about all I can say for sure is that larvae/medusae were likely carried in with some recent addition (water from a wild source, on the shells of Astraea snails, in bag water from another aquarium with shared livestock that was not (properly) quarantined by you, etc> What was its relation to the anoxic period, the algal storm and the copepod population changes? What kind of adult animal can we hope to find? and what should we look for? <time will reveal> I have feed the tank regularly with shrimp pellets waiting until previous offerings have disappeared. Right before the algal storm, and perhaps causing the storm, I fed with two Spirulina tablets that took weeks to disappear and only after they disappeared did the storm begin to clear. During the storm I did not feed because I was waiting for the tablets to be consumed. With such a heavy storm I felt that there was no lack of nutrients to worry about. After the storm cleared, I resumed feeding with shrimp pellets and weekly inoculations of DT. The water has since remained clear. I test regularly, but the water parameters are always perfect: Ca-400ppm, Total alkalinity-4.5meq/l. No measurable nitrate on a reliable nitrate test. <do allow some nitrites (5ppm) if you will keep corals successfully long term> Phosphate is low. I got these results even during the algal storm! I thought some mineral parameter must be off, but I guess that the nutrients must have been bound in organic molecules and not detected by the tests. Of all my tanks, this tank has, by far, the best test values. Also, there is no erosion of the live rock which I see in the other tanks even though I work hard to maintain calcium, magnesium and total alkalinity in those tanks. I have never needed to add any mineral supplement to this tank because the tests have always shown ideal values. (I suspect that the erosion of live rocks in the other tanks is associated with the use of calcium chloride in most calcium supplements. I have been experimenting widely with calcium supplements and I am not happy yet with anything that I have tried). <I strongly advise the daily use of calcium hydroxide with or without a calcium reactor. It is tried and try and has many benefits over other means of delivering calcium> I suspect that I tend and feed the tanks rather than the livestock. I don't have many fish: 7 in my 75 gallon and 2 in my 125 gallon. I am fascinated by the water and all the complex interactions between its inhabitants that it is my privilege to observe. I seldom intervene in the tanks except to try to provide stable conditions, light and a modicum of food. I am very interested in the zooplankton populations and have been toying with the idea of harvesting plankton from the Chesapeake Bay and adding them to one of my tanks. At night, when I go canoeing, that are beautiful displays of phosphorescent plankton and medusa. <yes... a marvel> I encounter them in small patches. Some patches are blue and some are green and seem to phosphoresce in response to being disturbed by the canoe. I would love to capture some of these and see what happens when they are placed in a tank. It is probably a crazy idea. <some are toxic as you may know... do be careful here> I don't know what animals I would be introducing, what their life-cycle would be, or what impact it could have on my tank. I would appreciate any warnings or suggestions for reducing risk that you might care to share. <all can/will be screened by the proper use of quarantine tanks for all things wet coming in... corals, fishes, snails, algae, live rock, etc... everything please> Thanks for your attention. I have really enjoyed reading the articles and FAQs. They seem very factual and have proven quite reliable. Karl <thanks kindly... wishing you the best. Anthony><<RMF lost the pic... pls re-send if you see this. Bob>>

Brown Hydroid Myrionema 11/17/03 Hi! I was wondering if you could tell me what is growing on this rock with my yellow Stars? See attached photo. <it is a fairly common nuisance hydroid, Myrionema... somewhat handsome looking to me, but is admittedly a problem... can be a plague. They will sting corals and clams and are invasive as you have noticed> They are spreading very fast. At first I thought they might the yellow stars just multiplying but they are brownish in color instead of yellow. Please let me know what you think. thanks Anj <alas, we are not aware of anything that consumes them yet (surely some organism(s) does/do). Manual extraction will be necessary and be mindful of not overfeeding the display which can fuel their growth. Anthony>

Myrionema... Brown Pom-Pom Hydrozoan 11/20/03 I sent you an email earlier with the wrong picture, sorry. Could you please identify what is growing with my yellow star polyps. They are more brownish than the yellow stars and seem to be spreading quickly. Thanks Anjanette <the organism pictured is unfortunately a nuisance Hydrozoan of the genus Myrionema. There are no clear predators on this creature to date that we are aware of... manual extraction is necessary. Also control nutrient that fuel it (skim well, do small frequent water changes, careful not to overfeed/overstock. Best regards, Anthony>

Cnidarian ID Myrionema - stinging hydroid 7/18/03 Hi Guys, <cheers> I have a very strange algae growth in my 50 gal reef tank (see enclosed pics). I think this stuff came in on some live rock I bought from a local reefer about a year ago. Now it is starting to take over my tank. <you have the nuisance hydroid Myrionema from the Pacific. It can sting and burn corals, clams, etc> I'm wondering if you know of anything to help me rid my tank of this stuff. <some limpets eat it> My parameters are: 50 gal reef (no sump) 4 x 96 watt PC lighting Remora Pro skimmer Approximately 65 - 75 lbs. live rock Deep Sand Bed 700 gph water movement (power heads) S.G 1.025 (refractometer) Temperature 79-82 F. Calcium 400 - 420 KH 7 pH 8.1 - 8.4 Ammonia/Nitrites 0 Nitrates 0 Water changes/top offs with RO/DI Thanks for any advice, Brian <some manual extraction may help as with a tooth brush tied to the end of a running siphon to scrub and suck the pest out without spreading it. Best regards, Anthony>

Hydroid hitchhikers 7/15/03 Thanks Anthony. The crab in question finally came out of the rock work again and I fished him out to take a closer look. Since I have the option, what do you recommend, keep hydroids out of the tank or put them back in? <in a big enough reef tank, I'd leave them in. Good water quality and they are unlikely to flourish> The ones on that crab seem to be the only colony. As for Aiptasia, I have had three very small ones that I first noticed about a month ago. They haven't got much bigger in that time and they certainly have not increased to plague proportions as I have read others report. < a good sign indeed. A well managed aquarium can have them in the display for years with little reproduction. Its all about nutrient control> However, I am almost to the point where I want to start stocking with inverts in earnest. Shall I remove rock and nuke them while I still have the chance or is good water quality enough to avoid problems later? <its enough... but then again, most people overfeed or overstock in time. Do remove the Aiptasia to play it safe. And be sure to QT all new inverts, rock, sand in the future to prevent such critters from coming into the display> By the way, my LFS has several rather large Aiptasia in their tanks. Should one always avoid buying out of tanks like that? <heck no! good husbandry means QT at home. You can screen most anything from there.> Finally, if you would be so kind as to offer a personal opinion. In general, would you expect the dual 6" skimmers driven with Rio 600RV's found on the CPR CY294 to do the job for a 170 gallon tank? <I think CPR skimmers can be tuned to work very well... but are not so low maintenance or effective as EuroReef's (idiot-proof and excellent). Aqua C skimmers instead are one of the very best values. Two I would put ahead of CPR skimmers> I expect to focus on inverts and lightly stock with fish. After running the tank for 2 months and with only a couple of LPS and a half a dozen small fish (5 Blue-green Chromis and a Sailfin Tang) plus a full complement of snails and crabs, the skimmer throats are thoroughly coated every day but I get very little liquid in the collection cups. Is that what you would expect with a light bio-load or should I be trying to produce more skimmate even if it looks a little on the pale side. This is my first aquarium, and I have no reference point for comparison. Regards. <no worries. Best regards, Anthony>

Hermit crab hitchhikers: Hydroids - 7/14/03 What's this growing on the hermit crab's shell? Please don't tell me it's Aiptasia. <no worries.. or at least, they are not Aiptasia. They are hydroids... and quite a handsome colony at that. Yet - they can be fiercely stinging and no less formidable to other invertebrates as Aiptasia> I do have 3 Aiptasia in a new tank that I have just begun to stock, but they don't look like this. <no worries about your glass anemones either... they only flourish in tanks with nutrient control problems (poor skimming, poor water flow, overfeeding, etc)> The ones I know that are Aiptasia are0.25-0.5cm across, brown and look just like the pictures on your site. The ones in the attached photo are much smaller, clear and growing like shaggy hair on their transport. Thanks. <do enjoy them in the meantime... a fascinating creature and one that will behave if you maintain proper water quality. Anthony>

- Hydroid Problems - Hello. <Hello, JasonC here.> How are you today? <Well, thanks for asking.> I have a 55gal. tank set-up for a little over a year with a Sebae, two clown Perculas, Zoanthid, a hairy mushroom, Sarcophyton, electric star polyps, various sponges (blue, red candy cane, and yellow), a green hard coral, 3 crabs, 8 snails, and a velvet damsel. I have PC lighting 6-65watts, new bulbs every six months whether they need it or not, CPR Bak Pak II protein skimmer and a calcium reactor. All have lived happy and healthy in this environment. About three months ago a friend bought me a sun coral. I quarantined it for three weeks to ensure it was eating correctly and content. I added the coral and three to four weeks later I noticed a lot of "feathers" in the tank on all of the live rock. I am positive it has been identified on your site... hydroids. <Egads.> I tried the siphoning technique but the base is so far into the crevices it reproduced 10 fold. My question is how bad can these things affect my tank? <Well... for their size, they are pretty potent stingers.> I am afraid they are affecting my Sebae. <Quite possible.> He is sitting up but he is not taking the food the Perculas bring him. His mouth is open slightly. I feel that if the anemone dies, the Perculas will die also. <Not so, they will be fine.> I have to save them! <No worries.> I assume the problem is the hydroids because the sun coral is non toxic. <All corals have the ability to wage chemical warfare.> I have not used any chemicals in the tank since it was formed. I tested the water: 440 ppm calcium, NH 0, pH 8.1 Alk Normal, NO3 0, NO2 .05. I am sure the NO2 are just a cycle. What can I do to get rid of the hydroids short of finding a sea dragon, Pteraeolidia ianthina. <Not really that east due to their size - you may have to extract the rocks they are on and remove the hydroids with tweezers.> I have not found a single supplier of them. <The sea dragon? Heavens no... these typically do very poorly in captivity.> If you can think of a single other reason for the eating habits of the Sebae please I am open for suggestions. <Consider more lighting.> My Sebae was a tank split and my tank mimics the conditions it was raised under. <Lighting as well? Most all anemones need intense lighting, and yours is likely not intense enough.> Please help. --Hydroid Hater-Tonia <Cheers, J -- >

Reproductive method of the Physalia physalis (Portuguese man-o-war) 5/20/03 Hi WetWebMedia, <cheers, Alex> I am a year 12 student currently doing a biology assignment and I have to compare the reproductive methods of the human to another organism. <one similarity is that we are both dioecious (separate sexes)> I decided to research the Physalia physalis and I can't seem to find anything that covers its lifecycle in enough depth. I know this organism reproduces asexually but I need to know exactly how it reproduces. <do a Google.com search with the genus name only and the rider "reproduction" and permutations of that word. I came across this link on the first page of hits: http://animaldiversity.ummz.umich.edu/accounts/physalia/p._physalis$narrative.html It would be much appreciated if you could answer this question for me. How does the Physalia Physalis reproduce? Thank-you Alex Brett
<best of luck, Anthony>

"Who was that masked man?" [Cnidarian ID] Right below the arm of the Atlantic gorgonian octocoral are some very fine anemone-looking creatures.  I'm not sure if you can tell from the picture, but they do not appear to be Aiptasia.  Instead, it looks like they are growing from very fine tubes.  In any event, it looks as if they are causing the polyps on the octocoral to retract.  Are these tube anemones?  Are they (otherwise) desirable? thanks tom <they are hydroids, Tom... a great nuisance... prolific and will burn many desirable corals and other creatures. Manually remove and be careful that overfeeding or messy feeding habits are not the cause of their current or future growth. Best regards, Anthony>

Portuguese Man O' War Dear WWM: <Howdy>        I was reading your Daily  FAQs and saw one on the Portuguese Man of War. Last year in the Dominican Republic I was snorkeling when I was stung by a jellyfish which looked like a balloon floating on the water with long blue purple tentacles. I went to hospital there and everything  has cleared up, but I never really found out what it was. The people there called it the "Life of the Water." I looked up man o war on the internet and there was very few sites. Thank You Bob Najdek <Mmm, might be the spelling. Try Portuguese... or the genus of this Hydroid: Physalia... and know that many other places in the world call this and other stinging animals of its kind by very different names... "Sailors by the wind", "Stingers"... By any name, no fun to get stung by. Bob Fenner> Removing finger-like hydroids Stinging hydroids have few natural predators that we can regard as reef-safe. If you have corals in the tank, it may be difficult to avoid manual extraction. In the meantime, you could try a stiff bristled toothbrush tied to the end of a siphon tube so that you could siphon slowly and scrub at the same time. We need to avoid fragmenting and spreading them. Bets regards, Anthony>

- Choerodon fasciata & little stinging hydroids - Dear WWM Crew, I have a 240 Gallon with approximately 70 pounds live rock.   On 11-22-02 I added a Harlequin Tuskfish "Tigger" that had been quarantined for two weeks with no signs of parasites or other.  I have noticed tiny Hydroid jellyfish (polyps) on the glass (dots with legs). At first I thought this was a really cool find from the live rock, but a few days ago I noticed spots on the pectoral and tail fin of Tigger, on closer inspection these spots really appear to be the Hydroid polyps.  Can these polyps attack the fish and be a parasite of sorts? <Not attack, per se... but if the fish bumps up against them... sure. But I will just add, as I also have a harlequin tusk, that spots on the tail are not uncommon. They come and go pretty regularly.> Tigger's color is bright and is eating well, and does not appear to be scratching or have any abnormal breathing. <Good deal.> There are not any other fish in the tank.  I am concerned about Tigger's health, the health of the tank, and about adding any new fish until I am sure these hydroid polyps are not going to cause a problem. <No fun... you may want to consider creating a scraper/siphon combination that would allow you to scape off a hydroid and immediately suck it out of the tank. You definitely don't want these floating around the tank. You may need to take more drastic action, I'm sorry to say. Hydroids are a pain - quite literally.> Your help is greatly appreciated!!    Thank You.  Jen Marshall <Cheers, J -- >

Once were once stinging celled animals are now doilies. Hydrozoan/Air Ferns Dear crew,  could you let me know what the e-mail address is of the people who harvest hydrozoans, air ferns. Thank you for your time.   Robyn <Gosh, it's been so long since I've run into these folks, companies. I would check on your search engines. Bob Fenner>

Lettuce sponge with feathers? Hi Bob! <Hello there> I have searched and searched through this web site but could not find anything similar to this problem... I have had an orange lettuce sponge in my reef tank for about 3 months now. It has been doing fine, but a few weeks after I got it, I started noticing a red feathery type of growth on it. The "feathers" continue to spread and grow larger, and I have no idea what this is. Is it a type of harmful algae, or just a natural part of this sponge? A turbo snail wandered onto it once and ate most of it off, but it just grew back. Any ideas? <Likely some type of hydroid. See here: http://www.wetwebmedia.com/cnidaria.htm  I might leave all alone... but am inclined to mention that if your sponge seems to be suffering from this growth, I might "snip" it off... with sharp scissors... with part of the sponge where it's attached... and siphon/vacuum out as much of the material as you can after. Bob Fenner> Thank you, Laura

Re: Air Ferns Would you think that the preservatives are starting to separate from the air fern. The organisms that make it are dead already because it out of the water. The air fern is like a coral. What do you think? Rob <The "air fern" are actually hydrozoans: Please see here: http://www.wetwebmedia.com/cnidaria.htm and the Hydrozoan FAQs linked beyond (where your other correspondence is archived... Could be the preservative, color is going away... supplanted with decomposers, space users on the surfaces... At any length, I would "pull them"... either try to clean them up, let air dry... or toss. Bob Fenner>

Re: Air Ferns I looked at my Air Ferns this weekend and the ones in the bright light are getting white spots on the stems and the branches are starting to drop off. I didn't see any change in the Air Ferns that are in the dark or the shaded light. Rob <I suspect decomposing organisms, other life forms are using the more brightly lit, likely warmer specimens for food, space. Bob Fenner>

Science Projects with Air Ferns Thank you so much for your help. This is for my year long experiment (8th grade). Rob Moeller <Ah! Will you be... culturing this colonial animal? I was a High School science teacher, so do let me know if I can help you in some way. Bob Fenner> > Thank you for your help. I think the class is Hydrozoa and the phylum is Cnidaria. I am looking for the order and family. I am leading toward the order being Hydrocorallina? > <No, Order Hydroida or Thecata... depending on differing schema.> > Would you know the order and the family. > <Sertulariidae according to my references. Bob Fenner> > Thank you again. > Rob Moeller > > Hi, > > I'm doing a science experiment on Sertularia argenta and preservatives. > Do you have any information on Sertularia Argenta? > > Rob Moeller > > Sertularia argentea Linnaeus 1758? Air Ferns are almost unknown to me. > > Unfortunately they have been utilized (treated, colored) as "ornamental  plants" for aquariums. Bob Fenner>

Air Ferns Thank you for your help. I finished my research and handed it in. When I started this experiment, I had thought the Air Fern was a plant and I was going to test the plant in light, diffused light and darkness. Now, that I have learned that I have coral with preservatives, I am testing the effect of light, diffused light and darkness on the preservatives. <Ah... interesting to see the differences here> Actually, I have learned a lot. Certainly, my experiment took a different twist. <As almost all do... and should!> I e-mailed the people who harvest the coral and they told me that the preservatives have glycerin in it. They also use green dyes in order to get the green color. <Mmm, more and more curious> The specimens in the bright light are starting to turn brown. <Likely algae growing on/in them...> Rob Moeller I was first e-mailing you from my Dad's account, but this one is my account. <I see. Be chatting. Bob Fenner> 

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