Horseshoe crab and purple urchins... OPublic'sMoney... mis-stocking 1/9/08
I work in a school where we have recently (6 months) established a 1000 gallon touch tank.
<Nice>
We have a large variety of damsels and starfish, arrow crabs, one lemon angel, live rock, cleaner shrimp, sally lightfoot crabs, flame scallops,
<Poor choice with the scallops, have a terrible survival rate.>
spiny urchin, polka dotted batfish, and about a dozen purple urchins and had two horseshoe crabs, about 9" in diameter. One died about three weeks ago and the other this weekend.
<Not surprising, are cold water species and would have trouble in the warm water required by the other residents. Please see here for more http://www.wetwebmedia.com/hshoesys.htm >
We added the urchins about three weeks ago and wonder if they are the culprit.
<Doubtful>
I fed the fish one evening on a weekend and found an urchin attached over one of the horseshoe's eyes. The eye was gone and the horseshoe was dead. Don't know which came first.
<The crabs death, urchin was just scavenging for a meal.>
The second horseshoe would not eat for me on Sunday of this week and on Monday it was nearly dead and the urchins were attacking its eyes.
<Easiest part to get to on the crab.>
Are the urchins the problem or do we possibly have another issue?
<Other environmental issues.>
Is it absolutely important for the horseshoes to be able to bury themselves completely?
<Does help them, but not the issue here.>
Our sand is not that deep. We now have two very small baby horseshoes that were added before the big ones died, but we don't want the urchins to get them too!
<The urchins won't but the inappropriate temperature probably will.>
We were hand feeding the horseshoes squid and brine shrimp and they were eating well every day. This was advised by the supply source where we purchased them.
<They should have advised you that they need different environmental parameters than the other inhabitants.>
I can't find any source of complete information on their care and would LOVE to have that information if you can point us to it. They are wonderful for the tank and the kids love them, but we don't want to just add another pair to have them die again in 6 months.
<The most likely outcome without a specialized cold water tank. See here for more http://www.wetwebmedia.com/horseshoecrabfaqs.htm >
THANKS!
<Welcome>
<Chris>

Re: Horseshoe crab and purple urchins  1/10/08
What is the "ideal" tank temperature for Horseshoe crabs...
<Something comparable to the wild, i.e., coastline of North America from about Delaware south to the Gulf of Mexico, but prime habitat is the warm-temperate parts. Think somewhere like the Delaware or Chesapeake Bays. So somewhat cool in winter, say 12-15 degrees C, up to the low 20s C in summer. They aren't tropical animals, and their lifespan is distinctly shortened kept under such conditions.>
and what is the ideal feeding arrangement??
<Again, just as the wild. Deep sand/mud, where they process food by shoveling it past their mouth as they burrow through. If you can see a horseshoe crab clear above the sand/mud, it's an unhappy animal. They plough through the sediment, and only really feed successfully when kept thus. They don't "hunt" for food like regular crabs, sniffing out stuff and gobbling it up. They're more like earthworms on land, in the sense that burrowing = feeding.>
We have our temp at 75 and had been feeding our guys by hand daily either brine shrimp or squid and the gobbled it down.
<Too warm, and does need to be seasonal, with lows in winter and highs in summer. Realistically, a room temperature tank in a cool part of the building is the ideal, and anything else will only shorten the life of the animal though heat exhaustion etc.>
We still have two small ones (2"). Is there any text you recommend for reading?
<Nothing much published beyond the article Bob already referred you to here at WWM. In labs, where Limulus is often used, it's a short-lived animal destroyed after the experiment is done. New stock is invariably collected from the wild.>
We are trying to develop a "library" for our students as well as internet sites they can research for information on our tank inhabitants.
<Much written on these animals, though mostly from biochemical and physiological angles, since that's what these animals are mostly used for. Not much on ecology, nor maintenance in captivity. Quite a bit known on breeding, but mostly from field observations. Do searches using its Latin name (Limulus polyphemus) plus those of the Asian horseshoe crabs Tachypleus and Carcinoscorpius spp. Cheers, Neale.>
(RMF, feel free to comment) ... the root problem/basis of many of our modern world's problems are derived, heated by their being too much government... people, money... resources stolen, mis-directed. Principally what we need is to do away with life-time civil servants... Think on this. RMF... who does see this as pertinent... the money mis-spent here...>

Re: horseshoe crabs
Hi I read the paragraph it seems its directed at only one species. I'm not sure what I have its light tan and about 2-3 inches in length I have about 7 inches in the back of my tank with lots of sand that he has left trails through would this be a small one that don't get big or a gigantic one? I told the pet store lady my tank was 30 gall long and she recommended him? what do you think. Thanks guys for all my question.
<Most all anyone sees in the trade in the U.S. is Limulus polyphemus... they do get large. Bob Fenner>

Horseshoe crab 3/19/04
I recently bought a horseshoe crab.  I've got him in my reef tank it consist of crushed coral and sand , it is mixed about half and half.  I was just looking around the net and had read that they do not do well in captivity because they usually starve.  I also read that they will eat different frozen foods that I can feed him but my main question is that if they die do they excrete a poison like the cowfish would when it dies. because I don't want it to harm my
other stuff in the tank. please help!!  thank you Angie
<Don't worry about the horseshoe crab poisoning anything else when it dies.  Yes, they often starve in aquaria for lack of natural food, but the bigger issue is that they are temperate.  Normal tropical aquarium temperatures are therefore stressful to the point of being fatal.  Best Regards.  Adam>

Horseshoe crab
 Dear Bob, <Michael here today, not quite as good, but I'll do in a pinch>
     I live in Rockport, MA and I'm going to set up a 20 gallon, room-temperature saltwater aquarium for local species.  It will contain local seawater and sand.  Some species I'm planning on having are mummichog minnows, common periwinkles, rock gunnels, and hermit crabs. <Neat - possibly some local alga as well?>  I was wondering if a store-bought horseshoe crab could survive in such a tank.  Horseshoe crabs are occasionally found in my area, but are uncommon and usually large.  I know feeding can be a problem, but I plan to use local sand from the ocean full of living things.  I could also use native seaworms.  If you have an comments, or suggestions for other species that could survive in such a tank, please reply.  <Well horseshoe crabs aren't all that difficult to keep alive, but they grow much too large for a 20 gallon aquarium.  The carapace of a horseshoe crab can be 12" across>
-Curtis  <M. Maddox>       

Re: Horseshoe crab
Michael,
Thank you!  I am amazed by how quickly you responded. <Thanks, thought I'm not always this vigilant>  If the horseshoe
crabs got to big, I'll just release them where I've found others. <As long as they're endemic to the area, and you release them when they attain ~5" they should do fine>  Do you know any good sites with horseshoe crabs? <I would search Google for some links for you but this computer is going haywire.  I hope I can even get this email sent>  Also, do you know if tidepool Sculpins or cunner wrasse could survive at room temperature?  Do you know of
any tropical species that could? <Depends what you mean by room temperature.  Most tropical fish will survive in 75-85 and do quite well>
Thanks again -Curtis <M. Maddox>

Horseshoe Crabs
I've recently ordered some small 1-inch horseshoe crabs for an established saltwater tank (with a few damselfish and a Hawkfish).
<I do hope that your tank is quite large (~180 gallons or more), as Horseshoe Crabs are unsuitable for life in a small aquarium, even if they are purchased small (everything has the right to grow, right?)>
The bottom is mostly rocky now, so I'm thinking I will need to make a sandy area for the crabs to burrow in, am I right?
<Yes, your assumption is correct.>
How deep should this sand ideally be for the crabs?
<Depends on their size. At a small size, I would think around 3" would be plenty. At adult size, you may need a couple of feet.>
Also, I've done a lot of research about diet, and have gotten quite a variety of answers. In your opinion, what works BEST with horseshoe crabs, and how often should I feed them (I know overfeeding can kill).
<They are detritivores, so fish food/krill would work fine.>
Thank you very much-- these are such weird creatures that it's hard to find specifics!
<I'm glad I could help. Mike G>

Horseshoe crab
I inherited a horseshoe crab. It has developed a black "fungus?" on its back (near the tail). It is approx. 6" wide and living in a 2 gallon tank...do you think it has outgrown the tank?
<Hello, the black fungus is probably algae that has grown from being in such a small tank. A horseshoe crab that size needs at least a 120 gallon tank. Good Luck MikeB.>

Crustaceans And Damsel Death - 08/12/2005
I'm wondering how my fish died; he was in a 10 g. tank.  He is a neon velvet damsel with 3 hermit crabs and horseshoe crab and a turbo snail.
<Way too much life for a 10 gallon tank....  Please see here on horseshoe crabs:  http://www.wetwebmedia.com/horseshoecrabfaqs.htm .  This animal is completely unsuited to your system.>
I had only had him for 24 hrs. and he was on his side.
<Almost certainly environmental.  Be testing your water regularly.>
When the hermit crab saw that he went over there and grabbed him so I took all the hermit crabs out in a small bucket with a bit of water and they ate that entire fish but the head. When they were done I put them back in the tank. Can you tell me if that was okay?
<Probably not a problem, in any case.>
My horseshoe crab has been buried for I think two or three days but has been messed with to see if he was alive.
<Likely not for long in your system....>
He was ,then he just buried himself again. Can you tell me the proper care for all of them? I would appreciate it.
Thanks,  Drew
<All you seek and more is already archived:  http://www.wetwebmedia.com/marine/index.htm .  Wishing you well,  -Sabrina>

Crustaceans And Damsel Death - II - 08/14/2005
I had read a few of your listings on horseshoe crabs would a pet store buy on from.
<Might wanna proofread before you send, for future reference....  I am *guessing* you are asking if a fish store would buy back your horseshoe crab?  Possibly, or possibly would take it in trade for store credit.  You will need to check with your local fish stores; all of them vary in what they will do about livestock.>
I don't know too much on the subject, I'm only 12.
<Ahh, you're doing outstandingly for 12!  Keep up the research, and you're sure to learn and enjoy this hobby.>
My hermit crabs are not big and neither is the horseshoe crab.  
<The size of the crab is not what's in question, just the pure unsuitability of it in any warm, small, tropical reef system.  The smaller the tank, the worse for the horseshoe.>
I have a little castle thingy and a little rock. I have also been cleaning the tank and doing water changes once a week. Should I keep on finding out if the crab is alive or to leave him alone.
<I would not mess with him any more than it would take to get him to a fish store or someone with a suitable system.>
I also don't have enough money to get a bigger aquarium.
<It would take a very large, cool water aquarium to keep the little guy alive.  Were I in your shoes, I'd truck him back to the store and ask for a refund.>
I haven't been able to find out about these little tiny things crawling on the glass is that bad or good and what do I do about them?
<They're more than likely good.  Probably copepods and other such desirable animals.>
Thank for all your help so far, you guys seem to know a lot about fish.
<The more you learn, the more you realize how much more there is to learn! What a terrific hobby this is.  I'm glad you're getting into it so young. I'd like to give you a few ideas for your tank.  If you stick with just invertebrates, like your hermits, and maybe a pair of skunk cleaner shrimp, it'll probably be a very easy, very fun tank to care for.  There are a lot of neat, smallish crabs (scarlet hermits, emerald crabs) and neat shrimp that you could choose from to make your tank fun without fish.  But you've got the right idea picking a single small, hardy fish if you do want to have a fish in the tank.  You're on a great road to a great start!>
Drew
<Wishing you well on this adventure of learning,  -Sabrina>

Horseshoe crabs  10/5/05
I was reading on your FAQ's about horseshoe crabs that they don't  live long ..days or weeks. I had kept them before in a tank without a  heater (room temp), and they lasted for years. I fed them black worms, and I  would put a little piece of fish under their shell. The tank was fairly warm,  but most of them did ok. <Eddie, the general rule for keeping horseshoe crabs is a larger system with fine gravel/sand and preferably cool water.  As you say, they are not hard to keep provided the correct conditions are provided.  James (Salty Dog)>   Eddie V.