Horseshoe crab arriving today, sys.  (RMF, thoughts on releasing Limulus into the wild? I'm against...)<<Am totally opposed. RMF>> 11/17/09
I read with interest your FAQ section on Horseshoe crabs.
<Fascinating animals indeed.>
Unfortunately, I did so after ordering a 2-3" crab yesterday from a website that said they are easy to raise and will do well in reef tanks.
<Good heavens no!>
I have a 125-gallon reef tank and a 55-gallon FOWLR tank.
<Not a good home for this chap.>
However, after reading your FAQ's, it is clear this new arrival will not be happy in either place due to the water temp, among other things. I want to give him the best shot at survival until I can figure out what to do with him long term.
<Very good.>
I have a 100-gallon Rubbermaid tub, 80lbs of Caribbean Live sand still in the bags, plenty of "seasoned" salt water and cured live rock, powerheads, etc. I will use whichever of these things I need to for this crab and will purchase whatever else you think I need for the next year, short of a new aquarium.
<Actually, maintaining Limulus under lab conditions isn't especially difficult, and if you Google "Limulus polyphemus" (the Latin name) as well as Horseshoe Crab alongside "maintenance" and/or "aquarium" you'll find there are fairly reliable protocols for keeping these creatures for extended periods. While not precisely white mice, they are much used lab animals, particularly for medical research. See for example, here:
http://www.nmfs.vt.edu/HSCwebsite/Projects/Laboratory%20culture%20and%20maintenance%20of%20the%20HSC.Lab%20Animal%20.pdf
In short, they're kept reasonably cool, room temperature in an unheated room usually fine, and maintained in a clean, filtered aquarium. Feeding is done separately, with the animal turned upside down, food (chunks of fish, seafood, etc.) placed in its "claws", and then the animal replaced in a tub of seawater. It's left to feed for about an hour or until its defecated, and then returned to the maintenance tank. Repeat every couple of days. In the wild these animals hunt for small organisms within the sand bed, but this really isn't viable in captivity.>
Please let me know the best way to set up these things to make a suitable environment for him until he outgrows the 100 gallon Rubbermaid (by the way, how will I know when he has outgrown it?). Also, can I release him into the Long Island Sound once he grows and if so, what size should he be before release?
<I'm not wild about releasing captive animals into the wild. For one thing, at any number of points along the chain of handling it can be exposed to parasites, bacteria and viruses that don't exist in Long Island Sound.
There's also the issue that you may not even have Limulus polyphemus, with Asian sources certainly sending out Carcinoscorpius to pet shops in Europe, and therefore possibly elsewhere. Obviously releasing non-native species is a bad thing. Since these animals do reasonably well in public aquaria, you might send a couple emails out to such places, to see if they can home your beastie. Alternatively, humanely destroy the animal (again, info on this will be in the scientific, if not hobbyist, literature).>
Lastly, would it be okay to purchase minced clams (like they use for clam sauce) and chop them even finer for him?
<A variety of seafoods is best, since by themselves seafood items tend to be lacking in one or other regard. Unshelled shrimps have calcium but too much thiaminase, shelled cockles are low in thiaminase but not enough calcium, and so on. The more variety, the less chance of problems. Lab specimens take standard fish pellets readily enough, and while there's debate about their use as a staple, as an occasional vitamin top-up they may have their place. Alternatively, your usual marine vitamin supplement could be used.>
Thank you for any advice you may offer.
Dennis
<Hope this helps. Cheers, Neale.>

Re: Horseshoe crab arriving today, more re sys.   11/17/09
Thank you for your prompt response.
<You're welcome.>
I will feed him/her as you propose.
<Cool.>
I will set up the Rubbermaid home for him/her for now. According to the seller, this is an Atlantic Limulus.
<Good to know. Telling the species apart isn't difficult, and a cursory review of the literature should help if you're interested.>
I have an extra submerged pump/filter setup from a small koi pond which I can use.
Should I leave the bioballs in there or just use the sponge filter?
<Probably won't make much difference either way. These aren't "delicate" animals provided they aren't starving or overheated (which are the prime sources of mortality in captivity).>
Will the crab be okay with the water movement that comes from the top outlet (used to be a fountain) of the pump/filter setup?
<These animals are used to very strong water currents, but that does assume they're able to "dig in" a bit. I'd see how you go. In aquaria they often get pushed onto their backs, in which case you'll need to right them.>
Should I fill the tub to the maximum level? (100gal)
<More water the better of course, but 100 gallons for a 3-inch specimen might be overkill.>
The only room I can put the tub in is heated. I will put a thermometer in the water. What is my target water temp? Should I do periodic water changes?
<Wouldn't worry too much. Unless the water temperature is above 20 degrees C, these animals aren't stressed. Do read that article I linked for you; it contains details on the established protocols.>
Lastly, should I not bother opening the two 40lb bags of Live Sand and just leave the tank with not sand?
<In labs sand is rarely used because of the risk of the sand getting dirty and causing infections. Since "clean" crabs are essential for the work being done, this is helpful. But under aquarium conditions a few cm of
coral sand and crushed coral would be very useful. Live sand is obviously helpful in terms of water quality management, but the Limulus couldn't care less either way.>
I also have Live Rock that needs a place to go. Can I put it in the crabs tub or should I put it in a separate tub?
<Limulus don't like rocks. Plus, below 25 C, your expensive Fijian live rock is soon going to die back. Would concentrate on old-school canister-type filtration, ideally supplemented with some aeration to keep
the water nicely oxygenated.>
Over the next few days I will do the research you propose so I don't have to ask you so many questions!
<I'm no great expert on these beasts, though like Bob, I've bumped into them a few times in the scientific side of my life. They're virtually never kept properly by hobbyists, hence the need to concentrate on lab reports.>
Right now, I am in a hurry to set up the crab's new home before FedEx arrives :))
<You'll be fine. These are EXTREMELY hardy animals when given essentially correct conditions. There is an Asian species sold as a freshwater horseshoe crab that manages to cling onto life for months under such
conditions, even though it's a brackish/marine beastie. Don't panic, do your reading, and enjoy.>
Thanks again,
Dennis
<Cheers, Neale.>
Re: Horseshoe crab arriving today
thanks again! I will give it my best shot!!!
<Good luck! Neale.>

Horseshoe crab, leave at the beach  8/9/09
Hello,
<Hi>
I have questions because of a very stupid situation, as probably evidenced by the title, that I need to resolve.
<Ok>
Recently my family brought home a live horseshoe crab this past Friday (along with about a dozen horseshoe crabs which died upon the touch of chlorinated water-- the horseshoe crab I managed to get some spring water for which I added salt).
<They are very sensitive to water chemistry, unless the salt levels are at the appropriate level, 35PPM, pH, and composition (marine salt not table salt) then they will quickly die.>
He is literally surviving in a clear plastic storage tub over this weekend, and we attempted to dump some sardine in there and now a piece of chicken, as well as one of the dead hermit crabs.
<I would not try to feed him, more likely to just foul the water.>
There is no sand of which to speak and I have changed the water twice since then. We are hoping to get him back to the beach today but we are wondering if we will end up shocking the crab, as many marine animals get easily shocked by temperature changes.
<Getting him back to the beach is his best and probably only chance, a difficult species to keep even or dedicated hobbyists.>
I've put the crab out on the fire escape in the hope that the water will more closely match the outside (I realize this is unrealistic but I still feel it's better than my guesswork).
<Temperature is probably the least of his concerns to be honest.>
Since I am assuming he ate neither the sardine or the chicken, we are also wondering how long he can go without food, and have we inadvertently debilitated him too long to survive upon his return.
<He can go several days at least without food, best to just get him back to the ocean as quickly as possible.>
Regards,
Joseph
<Chris>
Re: Horseshoe crab, 8/10/09
Thank you very much for your advice. He was returned today, and very quickly burrowed himself into the sand of the wet shore, which I assume means he is healthy enough to recover speedily.
<A good sign.>
<Chris>