Please visit our Sponsors

FAQs about Sea Urchins, Sand Dollars

Related Articles: Sea Urchins, An Introduction to the Echinoderms:  The Sea Stars, Sea Urchins, Sea Cucumbers and More... By James W. Fatherree, M.Sc.

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

Echinometra mathaei at night in Fiji

Supplementing Black Sea Urchin Diets Hello, <<Hello to you...>> Great site; as always. <<Thank you although I can't bask in the glory alone - this is the work of many people of which I am just the Garbage Scout Captain.>> I read up on your site concerning sea urchin diet.. (they eat anything apparently)? <<Not anything, but anything algae based... even coralline.>> I have reasonable green algae growth, and purple coralline is starting to grow as well.  What additional foods can I feed the urchin? <<Oh that is a difficult question because it's hard to clue them in - how does one ring the dinner bell for an urchin? You could leave things around but it's likely someone else more swift of foot and opportunistic will snag it. Best to just keep that algae growing, perhaps try to encourage other macro algae to grow in the tank.>> Do I put the food adjacent to it? <<You could try, but odds just as good that it would head in the other direction.>> Or under it or what? <<You see why this is not an easy question to answer... in your best interest not to disturb it so under it wouldn't work so well either. Best to just leave it to its own devices.>> I assume I would do this right before the lights go out? <<I don't think urchins care so much... my tuxedo urchin is busy 24/7.>> Thanks again Bob, you are the ANSWER MAN!! <<Wait! I'm not Bob... what does that make me?>>  Marc <<Cheers, J -- >>

Tuxedo urchin I got a blue tuxedo urchin (Mespilia globulus) yesterday. About ten minutes after being in the tank, it made a beeline for the front glass, and crawled up it. It won't come down from the glass, it slowly works its way around the tank, and right now its on the side of the powerhead. Is there any way to entice/goad it down? <yep...Jack Daniels and cigarettes... Thanks for asking> <PS... they often explore their surroundings for the first days/weeks...patience my friend. Anthony>

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. Thanks, Craig <You are welcome. -Steven Pro>

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 -- >>

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 -- >>

Chiller, lighting, and sea urchin question! <<Greetings, Kevin, JasonC here... >> My tank is about 80-82 degrees and I was thinking I need to get a chiller or maybe some cooler lights cooler lighting unit). <<80-82 isn't really out of hand compared to conditions in the wild.>> I have a 150g tank with 2 fluorescent hoods and they don't have any ventilation. Can I get a good light that has ventilation? <<Why not do a retro-fit and add some ventilation, fans, etc?>> I was looking at the power compact lights, any ideas on those kind or any other kinds of lights, I need something soon! <<All lamps produce heat, it cannot be avoided.>> Is a chiller necessary to reduce my tank temperature just a couple degrees, they're very expensive, but in case I do get one, do you recommend one? <<I don't generally recommend chillers unless you live in a desert or are attempting to do a low-temp system; something less than 75F. Usually a one or two degree pull-down can be easily accomplished with one or more fans blowing over the surface of the tank to produce evaporative cooling, or placed in the light hood to evacuate the warm air.>> I liked the idea of the coil that sat in the sump! <<Honestly, those are a very poor design and not worth the money.>> And lastly, I have a sea urchin that I've had for a couple years and he's losing his spines. I've heard that when this happens it means they are going to die and they should be removed from the tank. <<certainly a sign of declining health.>> He only has the bottom half of him that have the spines! What should I do? <<Perhaps crush it and feed it to the fish if you have triggers or wrasses, or just toss it out.>> Thanks for all your helpful advice you always give me, you're the best! -Kevin <<Cheers, J -- >>

Sea urchin question Hello all! I have a question about this urchin that my LFS said ate just sea veggies. I've attached a photo. Could it possibly be eating my feather dusters? I have seen it on top of them and then the duster shed it's plume, and I've also seen an empty tube after the urchin had been there. I've had the urchin for about 3 months. I was told it was a pincushion urchin. true? Thanks for your wealth of info!! Stephanie <Whoa! This may be an Asthenosoma spp. or possibly a more innocuous Tripneustes spp... take great care, as this animal may well be toxic/venomous to you! Do enter both genera in your search engines and try to identify this specimen. If it is of the former genus it IS an indiscriminate omnivore, it may well have eaten your other sedentary invertebrates. Bob Fenner, who encourages all to investigate livestock purchases before buying!>
Re: sea urchin question Bob, I have identified it as Asthenosoma spp which is a "fire" urchin. ehhhhhhhhhh!!!! <Yeeikes! I thought as much... be careful. I photographed a gorgeous one a couple weeks back in the Red Sea... and took great pains to avoid... great pains!> I really appreciate your help in identifying. He must've had my dusters for lunch.
<Keep your hands clear of it to be safe. Bob Fenner>

Urchin question from Steve Bob, I have a question about one of my customers tanks...she is a doctor doing research on human cancer studying sea urchins. One of her test subjects is a 55 gallon tank housing 25 Strongylocentrotus purpuratus.  <A local (Southern California) species... the most common (Purple) Sea Urchin off our coast> They came in last Wednesday and everything was fine through Saturday, but on Monday everyone was dead. <A very common test subject and too common occurrence> My gut feeling is that the chiller (20 yr. old Aquanetics unit) may have gone bad and killed the urchins, but could it have been the acclimation process?  <Yes... I suspect a "residual" damage effect from the shipping process itself> The urchins come in with ice in a Styro packed between wet newspaper- so I can't drip acclimate them. Would that have done them in? Being active for four days and then just dying? <They could even have drowned... much to say here... next time, move the ice to your pre-made synthetic (best from the system...) and do airline siphon drip this onto the "warming" urchins... eventually rising over them (does take a couple of hours)... add airstones and let water warm to the system temp. overnight if necessary... throw away this acclimation water... moving the urchins underwater in a jar to the main system> I (Deb) am typing this for Steve while he is at this clients office. Whenever you have the chance to answer, I will call him. <Real good. If he has questions, problems, wants to bounce suggestions about, have him call, email me.> Have a great day, Deb (and Steve) <You as well my friend. Bob Fenner>

Urchins Follow-up Deb missed one part in relaying the story from me to you via email. The urchins were shipped dry.  <I understood this to be, know it to be so> There was regular, tap water ice in a plastic bag laying in the bottom of the Styrofoam. Then a layer of wet newspaper, then urchins, and then more wet newspaper. Do you know how hard it is picking newspaper pulp off of pointing urchins? <Yes... have done it many times> I was concerned with these deep water animals being exposed to air, but the Dr.'s said it was ok and normal for their shipping. <Yes> The reason I mentioned the chiller was last week before the urchins came in we had some weird weather and it got up to 80 degrees out. The lab temp rose to 82 because the AC was not on yet. The old chiller had a hard time keeping up and allowed the temp in the tank to go from 46 to 54. I was concerned that the chiller was going to be a goner, but the urchins were already being shipped by the time it was discovered. The weather has returned to normal now and the temp was back to 46 by the time I unpacked the urchins. Talk to you later, Esteban <Do keep my notes re a drip/acclimation protocol on hand... about the best "any-arrival-shape" procedure... as you'll find. Bob Fenner>

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>

Sea Urchin Research Mr. Fenner, <<Mr. Fenner is away diving, and I am here answering what bit of WetWebMedia mail that I can. Bob will be returning on 12/7 and I'll save this mail so he will read it and get back to you. In the meanwhile, do try www.fishbase.org although I'm not sure if inverts have made it in there yet. Cheers, J -- >> I came across your website, and was pleased to find a site that could answer many of my questions on sea urchins. I am researching the species, Astropyga magnifica, for a project I am putting together and I am having difficulty finding the complete classification, from kingdom to species. I was wondering if perhaps you knew of a source where I might be able to find this, and other information on this specific species, or if there was anything you, yourself, could tell me. Any help that you could give me would be very much appreciated. C. K. Spengler <<Let's see... Kingdom Metazoa, Phylum Echinodermata, Class Echinoidea, Family Diadematidae, genus and species you give. RMF>>

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>

Sea urchin erupting?...sort of! Hello Bob, <Anthony Calfo in your service> We have what I believe is called a Diadema savignyi sea urchin.  <AKA Blue Dot long spine sea urchin> It is black and you can see bright blue in it's body at night. anyway...last night he seemed to have some kind of volcanic eruption. All of a sudden about a million (ok that might be a little exaggerated) tiny white pebble like things rushed straight up and out of his head (or top of him). At first I thought it might be some kinds of eggs but it really looked like tiny bits of rock. and the worms who caught the pieces quickly spit them out with no interest at all. What exactly was that and will he do it often?  <excrement...and yes, as often as necessary> Is he special, should I send him to David letterman? <possibly... I have yet to see a powerful, pooping prickly sea urchin on his show just yet> Christina <thank you for the smile... I think I learned this tidbit the same way more than a few years ago. kind regards, Anthony> ps: you usually get much more educated questions from my husband Pat. I really had no interest in this whole fish tank thing until one day I went to a very nice Aquarium and came home with our first creature...a little blue leg hermit. I then realized that sea creatures were extremely interesting and entertaining. (and my husband is learning that they are very essential to any tank) so.. now we are in the process of setting up a reef tank so I can have zillions of creatures! I was starting to throw my husbands tank all out of whack.

Sea urchins I tracked down your website after reading over the reviews of your book on Amazon.com. I've ordered the book, but, according to the index, it looks like there are only a few pages specifically dedicated to sea urchins. <Yes> I've been reading the site as well, but thought maybe I'd try asking directly. I'll summarize the background below, but basically my questions are: 1. Are there any changes in conditions that can be used to help coax urchins back to health? For example, do slightly warmer temperatures help? <Depending on species, yes... or lowering... often troubles with a lack of alkaline reserve, biomineral concentration... but the vast majority of "reasons" for mortality are cumulative insults from collection, handling...> 2. Is it possible to keep an urchin-only tank, or do I have to create a full-scale marine aquarium? <Very possible to have a "species" or "concept" tank... often done in the sciences for demonstrations (embryology principally)> 3. If urchins become ill by developing spots and losing spines, is there any way to successfully treat them? <At this point, usually lost... but there is always hope... environmental modification, soaking in antimicrobial compounds...> 4. What is the recommended long-term diet for sea urchins? I've used a combination of algae and "urchin cookie" (containing carrots, egg, egg shell, gelatin) and invert food - but I'm not convinced this is the best. <Mmm, once again... species dependent. A good idea to encourage you to do a bit of look/seeing of the scientific literature. Please read here: http://www.wetwebmedia.com/litsrchart.htm> Basically, my problem is that I need to coax some urchins back to health and my situation may be a little different from normal invert acquisition and setup. I've talked with urchin researchers and with people at the Chicago Aquarium, but seem to find that there is very little information available. <Not much in the hobby literature, the Net, no> Unfortunately, I teach an embryology class and sea urchin embryology sets seem to be designed to be completely disposable (I have complained to the suppliers, but it doesn't seem to get me anywhere). <Ahh, you don't have to toss the animals after extracting gametes... can be rinsed, coaxed back to health> I'm trying to keep all of the urchins, but obviously they get off to a bad start by being shipped cross-country and then injected with KCl (I'd planned to use electrical stimulation, which is less harmful, but received a species that can only be stimulated to release gametes using KCl). <This is S.O.P.> Anyway, I used minimal KCl and the six urchins are currently recuperating in a 20 gallon tank with a canister filter, protein skimmer, and 1.020 salinity. <Mmm, I would keep them in nearer to 1.025 spg> I also use water that has been filtered through a Tap Water purifier, then reconstituted - plus I added Dechlor treatment to the water about a week before the urchins were placed in it. The last time I tried to do this, the urchins did well for about 7 months, then developed some type of infection, lost spines, and died despite treatment with Chloramphenicol (recommended by some urchin researchers) <Yes... but/and do to aplastic anemia concerns, not available directly to the public... Posted for browsers> and isolation of sick urchins. I'd like to avoid repeating that experience if possible. If necessary, I'll set up a proper marine setup - but what do I need to have in order to allow the urchins to survive? By the way, the urchins are L. variegatus. <The genus and site of collection please. Bob Fenner> Do you have any suggestions? Thanks very much. -Ann

Re: sea urchins Thanks very much for your prompt response. I appreciate the input (I'm a herpetologist; I know little about aquaculture). <Yikes... and have spent many happy and zany moments with herp types... our grad school had the typical arrangement of reptiles, amphibians and fish collections in one building... many non-denatured alcohol and OJ drinks instead of holo- and paratype specimens solutions... Oh, and of course the ASIH...> By the way, can I request that you delete my signature line if you post my message?  <Yes, certainly. Will make sure is done> I wasn't thinking about my message being posted and didn't mean to include my signature line, since I don't want to represent my institution as a whole when asking for urchin info on the web... Thanks. <I understand> > By the way, the urchins are L. variegatus. > <The genus and site of collection please. Bob Fenner> Unfortunately I can't tell you - I didn't collect them myself (Note: I hope to keep a healthy population myself in preference to future collecting anyway, if I can get the husbandry down). <But at least the genus, "L."... is this Lytechinus? Bob Fenner> Thanks again. -Ann

Re: sea urchins > instead of holo- and paratype specimens solutions... Oh, and of course the > ASIH...> Oops - I just realized that I said that "Indianapolis was fun," when that was HL/SSAR... ASIH was at Penn State! There were too many meetings last year... but all were good. <Ah, academia! Bob F> -Ann Re: sea urchins > <Yikes... and have spent many happy and zany moments with herp types... our > grad school had the typical arrangement of reptiles, amphibians and fish > collections in one building... many non-denatured alcohol and OJ drinks > instead of holo- and paratype specimens solutions... Oh, and of course the > ASIH...> Yes, I'm regularly at ASIH... Indianapolis last year was fun! We had one fish person at grad school - but hearing about the otoliths of introduced cichlids didn't give me much information about aquaculture. We were a herp-intensive group. I have a large assortment of herps that I've kept for many years, but urchins are my first venture into real aquaculture. I wasn't willing to throw out the urchins after embryology lab, so I've had to learn a few things since then... I'd never heard of a protein skimmer before. <Yowzah, talk about jumping en media res!> > <But at least the genus, "L."... is this Lytechinus? Bob Fenner> Yes, it is. I believe that they were collected somewhere near the Florida Keys, but I really don't know. I think that Lytechinus variegatus is found around the Keys, these urchins are supposed to be L. variegatus, and these urchins were shipped from Florida. Thanks again. -Ann <I see. Well, this is a relatively hardy species... even stressed, washed with potassium chloride soln can "come back". 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>

Sick urchin, missing fish Hi Bob, <Actually, you have reached Steven Pro. Anthony Calfo and I are helping Bob with some of the daily questions.> I have had a blue variegated urchin for over a year, and it is losing its spines. I also have a royal Gramma, and it is nowhere to be seen. The Gramma is an extremely good hider, however, so I don't know if it is dead and eaten (hard to believe in this short a time) or if it's feeling sick and hiding. Yesterday, the fish was out and about and I noticed nothing untowards with the urchin. Yesterday, I installed a new Maxijet 1200, and I topped up the water levels to compensate for skimming (about 2 gallons added). 10 days ago, I installed a new lighting canopy, and it has caused temperature to fluctuate from 72 (low) to 78 (high) when it is on; my old lighting system did no such thing. <A daily 6 degree temperature swing is going to be highly stressful to your animals. I would address that first and begin to look at water quality parameters; pH, ammonia, nitrite, nitrate, etc.> Five days ago, I purchased two new snails, nothing fancy, and a giant Fanworm. Those are all of the changes I've made, and now I have an urchin in danger and a lost (?) fish. I wonder if you have any ideas what it might be? <See above comment on temperature> Again, this happens shortly after installing a Maxijet 1200. I know you routinely put these into service without intensive rinsing, but I'm starting to think twice bitten... I'm including the email I sent you the last time this happened. Is it possible that there could be a manufacturing poison on the Maxijet? <I find this doubtful.> Are any of the other changes suspicious? I hate losing valued pets like this, it really makes me sad. <If you respond, please include exact numbers for the water quality parameters you checked.> Thanks for any help, Paul <You are welcome,> <Steven Pro>

Sea Urchin Good Evening, <And to you> Two quick questions .... 1. I believe I have a small Sea Urchin in my 90 gallon, 2 month old tank. It came with the cultured live rock, it is as large as the end of your small finger, black, and has spikes sticking out all over. Hides all day and comes out at night. Seems to be growing quite a bit. Is this an OK resident? Can't seem to find much info on these things on the net. <Likely fine. Please see: http://www.wetwebmedia.com/urchins.htm Something like the Diadema shown?> 2. How do you feel about Activated Carbon, and how often should I change it? As usual I hear pros and cons. I have a TidePool Bio wheel sump system, with one tray of AC. Thanks for your excellent resources. <Please read here: http://www.wetwebmedia.com/carbonfaqs.htm You are welcome my friend. Bob Fenner> John Kummer

Sea Urchins Bob, I have a relatively new 180 acrylic reef tank. It was upsized from a 150. I have some green hair algae, more than I would like. My three tangs won't touch it. I am thinking about buying a couple urchins for control. Will urchins scratch acrylic? <They can, but not usually... but there are other avenues of algae control I would engage... please read: http://www.wetwebmedia.com/algaeconMar.htm and the links beyond> If not which ones would be the least damaging bulldozers? <Please read the pertinent sections of WWM re. Bob Fenner> Thanks, Jim

Sea Urchins Mr. Fenner, I came across your website, and was pleased to find a site that could answer many of my questions on sea urchins. I am researching the species, Astropyga magnifica, for a project I am putting together and I am having difficulty finding the complete classification, from kingdom to species. I was wondering if perhaps you knew of a source where I might be able to find this, and other information on this specific species, or if there was anything you, yourself, could tell me. Any help that you could give me would be very much appreciated. C. K. Spengler <Mmm... let's see o ECHINOIDEA (merisiilit) |--o PERISCHOECHINOIDEA | `--o CIDAROIDA | |-- Cidaridae* | `-- Psychocidaridae* `--+--o EUECHINOIDEA ()? [paraphyletic?] | |--o DIADEMATACEA | | |--o ECHINOTHURIOIDA | | | `-- Echinothuridae* | | |--o DIADEMATOIDA | | | |-- Diadematidae | | | |-- Lissodiadematidae | | | |-- Micropygidae | | | `-- Aspidodiadematidae  Genus Astropyga is a part of the Family Diadematidae... Bob Fenner>

Sea Urchin Question Mr. Fenner- My question relates to the use of Sea Urchin (Uni) as food in sushi bars and Japanese restaurants. <You know... as a kid in Japan I always wondered what Sea Urchin roe tasted like (too expensive for me then), and then when I moved to the source (Southern California) of a good deal of it, I couldn't understand what the big deal was/is... "Oh, you just haven't had it really fresh", I can hear my friends saying... Oh yeah? I've cracked Strongylocentrotus sanfriscanus tests open underwater, taken out my regulator mouthpiece and eaten it then/there... it is better fresh... but still tastes like "the bottom of a boat" to me (and don't ask me how I know what that tastes like, hee hee!> Can any toxins at all be absorbed into the human body from eating Sea Urchin/Uni the way it is served in Japanese restaurants? (Liver, stomach, pancreas, etc.) <Oh... I imagine there is some possibility... The biggest threat in my opinion is likely from "herring worm disease" (anisikiasis)... have a bit about this posted on our site, here: http://wetwebmedia.com/roundwor.htm Or, much more likely, liver disease from too much sake and good Japanese beer. Mmm, I'm getting thirsty. My point is, there's probably a greater risk from breathing car fumes getting to/going from the sushi bar than ingesting sea urchin eggs. Bob Fenner. Oh! And should mention, these are used in many fish foods.> Geoff Williams

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>

Sand bed Hi, Bob and good evening. I'm still confused about this sand bed and live sand. Somebody on the net tells me now that the live sand my dealer sells has only bacteria in it, but none of the important "critters" that I need to get the sand sifted. <This is possible. There are such products.> They suggest that I put 3" of sand collected on our beach on the bottom. Then 2 bags of the live sand from the store and on top of it 1" real live sand from our beach collected in 3' of water. That would give me all the critters. <A dangerous proposition... pests, parasites, pollution too likely present. I would just use some live rock with whatever source of substrate... the LR will inoculate it fine> Can any phosphate in the sand be filtered out later? <Mmm, yes... or bio-accumulated.> I might find a stretch of more or less clean beach not too far away, but we still have rivers and the city polluting the ocean. I find a lot of 'sand dollars' close to the beach in the ocean. Is that a sign of good water? <Not necessarily> Can those animals live in a tank. <Yes. There are public displays of these echinoderms about. And many labs utilize Sand Dollars for research...> I never read anything about them. They bury in the sand. Why the big difference in the depth of a sand bed. Will a 1.5" bed not work biologically? <Depending on depth, chemical make-up, angularity, s/b fine. Please start reading here: http://wetwebmedia.com/marsubstr.htm and here: http://wetwebmedia.com/livesand.htm> Now that I have solved my problem with the temperature, I have another one. I had 2x20 W and 1x15W bulbs on my tank, but now I can fit only 2 x 20 W light fixtures on the remaining glass covers. The rest is open for ventilation. Will 2 x 10 000 K bulbs be enough for the FO tank? <Yes. Bob Fenner> Thanks, Bernd

Re: Sand bed Hi, Bob. Thanks again for Your well appreciated help. I now have enough new stuff to read. Good night. Bernd <Chat with you soon my friend. Bob Fenner>

Unknown species and an urchin Dear Mr. Fenner: <Hi Samantha, Lorenzo Gonzalez standing in for Bob, who's on fish-safari in Indonesia> I had written to you sometime ago regarding an unknown (to me anyway) species of sedentary mollusk. I have since taken a few pictures of the creature, but unfortunately my scanner is not working and so I'm presently not able to send photos via the net. However, it is possible for me to send the photos via snail mail if you have an interest (I think the resolution of the photos is much better than the scans anyway). If you are interested in receiving pictures, then just let me know an appropriate address. Otherwise, I'll pass them along when I have a new scanner. <Bob seems to get digital shots or scans occasionally via email, and usually they're good enough to identify an animal. But sedentary mollusks can be particularly hard to ID. I'll let him decide... he's back on the 12th> A second question that I had is whether you know the approximate life span of sea urchins.  <I've seen them several years old, and a nearly foot across...> I don't know the precise designation of the species I have, but it is deep purple/blackish from Florida, with long spines. It has been living in my tank for a little over a year now and seems quite happy.  <They're usually pretty easy, most chemical treatments will kill them in a flash, though. So will a hungry triggerfish... :-) > However, since it is getting quite large and my tank is small (15gal) I'm starting to worry about its natural life span. Any info you could give would be very helpful. I'm going to be setting up a larger tank towards the end of the summer and I could move the urchin to that tank once it is set up. <That'd probably be fine.> Current tank info: 1.25 yr old, 15 gal, ~35 lbs live rock (aquacultured from Florida), CPR back pak filter, maxi jet powerhead, lots of mushrooms and assorted soft corals (e.g. star polyps, etc), 3-4 xmas tree worms, a colony of little white feather dusters, 2-3 Chitons, a sea urchin, several small brittle stars, 3 hermit crabs, 2 tank raised ocellaris clowns (> 1 yr old), and one female spotted mandarin (> 6 mo.s in tank, she eats lots of stuff including frozen brine shrimp). <Boy, that sounds like a VERY nice little tank. Definitely a success, and certainly nicely balanced, if it can support that mandarin. And you're lucky to get one that eats frozen food. (Be sure she eats a variety, and/or you feed a vitamin-boosted brine... brine-shrimp are to fish what sunflower seeds are to birds, and Twinkies are to humans... Best regards! Lorenzo > Samantha Harris, Ph.D. Postdoctoral Fellow Department of Physiology 1300 University Avenue University of Wisconsin-Madison

Re: unknown species and an urchin <Sam, if you've already kept another Mandarin, in so small a system, for so long a time, and your current friend is doing so well... you're doing everything right, perhaps with a small shot of luck on getting robust fish to begin with! - I don't think I'm in any position to advise you! As far as Cyanide collection goes, Bob would know for sure, but I doubt you'd need cyanide to catch these guys. They're a little shy, but not too terribly defensive, as few big fish will eat them (poisonous/taste bad). :-) Cheers, Lorenzo> Hi Lorenzo: Thank you for getting back to me in Bob's absence. It must be rough- a fish safari in Indonesia! I'm envious! <<Was indeed a blast... get my pix back from processing later this AM, can't wait. Bob F>> Anyway, thanks for the info on the sea urchins. It sounds like mine has a while to go before he gets old. Regarding my little mandarin, is there any brand or food supplement that you recommend? Also, I know that the mandarins have a reputation for being hard to keep, but she is the second one that I've gotten to eat frozen food. The first one I kept for about 3 yrs in a 30 g tank with about 30 lbs of live rock. They actually seem quite hardy. Therefore, I was wondering if their difficult reputation might be a result of poor collection practices (e.g. cyanide or some such device) that affects their ability to survive in captivity? Thanks again for your time Sam Samantha Harris

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>

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 Urchin Hi Mr. Fenner, <Howdy> I have been researching this hobby for about 5 months now and just now getting started.. I purchased 20lbs. of live rock (from the Gulf) from my LFS and I have seen 2 sea urchins and was wondering how to remove them without harming them, but keep the nice flat rock they inhabit. <Place some foodstuffs you think they might be attracted to (like some sheet algae from the oriental food store/section tied to a stone in a strip (like with a rubber band) near them... and wait till they more off> Also on the same rock I want to remove 2 cone snails and a Limpet. Can you suggest a way to do this without harming the animal.. <The cones I would just move forward/backward by hand net... the Limpet... more difficult to extricate... gingerly with a knife that is sharp only on one side. Quickly slid, sharp side down under the foot...> Thanks for your advice, Chris Thompson <You're welcome. Bob Fenner. Who has removed many Archaeogastropoda like this... to eat them!>

Purple pin cushion hi bob, how are you? thanks for all the great advice you have given me. I have a question about a purple pin cushion I have. no one seems to know much about them. I noticed all over the tank a bunch of little needle's. I thought they were coming from the crabs waste. then this morning the pin cushion was down on the sand and it looks like it has lost half of its tentacles. it moves around the tank three or four times a week. is this normal or is it dying? james <Not good for this animal to be losing its spines... something doesn't suit it... temperature (some are from cool/coldwater... alkalinity, biomineral off... lack of nutrition? Take a look through v. 3 of the Baensch Marine Atlas, other works for i.d. and plug this scientific name in your search engines. Bob Fenner>

My new red sea urchin Hello Mr. Fenner: I am a beginner aquarist who has recently setup a 55 gallon tank. The biological filter is established and the water quality is excellent by all of my tests (NH3, NO2, NO3, specific gravity, pH and water hardness). I am inquiring about a recent addition to my tank. I currently have 3 Firefish, 1 blue damsel, and my new red sea urchin. I was told by the aquarium supplier that it is a red pencil sea urchin that would assist in reducing my tank algae, but it doesn't look like any of the pictures that I've seen. It is a mottled red-purple-tan color, with short, dulled spines. There is a picture of what it most closely resembles at www.coolmoose.org/fish.htm. <Yeah... I make this almost assuredly out as a Eucidaris metularia... and yes, it does eat attached algae... but wouldn't have expressly sold/suggested this as a/the algae eater for this system...> Anyway, my question is, it seems to have these white, squiggly looking attachments partially covering its spines. These attachments are open at one end, circular with fanned out filaments that crown the open end. Is this some sort of parasite, or is part of the actual sea urchin? If it is a parasite, how would I treat it? <Wow, you've got good vision! This is part of the Urchin, no worries> If I can provide any other information, please do not hesitate to ask. I'm going to look for a good encyclopedia of marine fishes, invertebrates, echinoderms, etc., to assist me with my questions. I just haven't found a good one yet. Thank you in advance for your assistance. <There are a few... not just one... (It would be a real bicep builder!)... Do check on the listservs, the www.WetWebMedia.com site's Links pages for input for reference works... If you have the funds, Scott Michaels "Reef Fishes" books are very nice, The Modern Coral Reef Aquarium for their first three volumes in English (a fish one is on the horizon) for invertebrates in captivity, and the Baensch Marine Atlases in three volumes as well... have all of these (and a few others) within arms reach. Bob Fenner> Deborah H. Colella

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>

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 

Hi Bob My Sea Urchin is sickly Bob, I have had 2 sea urchins in my 90 gallon tank. Recently one of them has  been dropping its needles and has what appears to be a red/purple sore in one  spot. The other one is fine however. what should I do? Thanks, Adam >> I would pull out the one that is dying... (in a container, don't lift the animal into the air), and place it in a quarantine set-up... Bob Fenner

Sea Urchin Hi I recently purchased a sea urchin for my tank which contains some corals, clown fish, snails, shrimps an hermit crabs. However I'm concerned as to its eating habits. I currently feed flake food and pellets. From what I can understand, they normally feed on algae and plankton of which I do not think there is enough. I can buy jars of Zooplankton - would this be suitable ? Thanks in advance. Ghufar Razaq >> Instead, get your hands on some "sheet algae" from an oriental food store (or that section of your Supermarket)... and place a part of this down near the edge/under the urchin... Most species are macro or micro-phagous herbivores... they eat small and large algae in the wild. Bob Fenner

Unidentified Urchin Hi, Bob: I recently couldn't pass up a beautiful "blue-dot pin cushion urchin" from my  LFS. He is about 4" in diameter with blue dots which fluoresce. I was told  the critter is venomous.  I was wondering whether you've ever heard of such a creature, and if you  could tell me, though I don't plan on touching him, just how venomous it is  (i.e., death, pain, etc.) Thanks for your ever-helpful advice. Marilyn >> Yes, there are many such colored species of sea urchins... and yes, they are venomous through their tube feet... but not very dangerous to you. Far more of concern are physical injuries from their sharp spines. Take care if you have to move one of these biological pincushions to utilize a net... and not lift it into the air (in other words, scoot the urchin into a container underwater... Bob Fenner

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

Become a Sponsor Features:
Daily FAQs FW Daily FAQs SW Pix of the Day FW Pix of the Day New On WWM
Helpful Links Hobbyist Forum Calendars Admin Index Cover Images
Featured Sponsors: