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 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>

Spiders with Shells?
hi there,
<hello! Ryan with you>
I want to know where I can buy the larger sized dried horseshoe crab shell (more than 6 inches wide).  my interest is to paint pictures on them.  so I would want the smoothest-surfaced variety available, rather than some I have seen online that are quite craggy in topography.  what is a fair price for these shells.  I am in California, are there any available here, or would they come from the east coast?  I am seeing them priced at $20 and up plus shipping and handling.  this seems high to me.
<Horseshoe crabs, provide a habitat for many smaller crustaceans- Barnacles, Mussels, etc.  This is likely why they're not always a "Paintable" surface.  The shells of these unlikely arachnids also contain Chitin, a chemical used to speed healing.  Lysate, also found in their bloodstream, is used to treat spinal meningitis.  Add the fact that they are a member of the endangered species list: This is why they're highly valued.  I'm sorry that I can't point you in the right direction for a retailer, but one doesn't seem to exist.  Perhaps a running wanted ad on Craigslist.org is your best bet? Cheers, Ryan>
thanks for the help,
Dave

- Vanishing Horseshoe Crab -
Hello, sorry to bother you once again but I have three quick questions.  I put a baby horseshoe crab in my 44 gal about 4 days ago and I haven't seen any signs of him since.  My inhabitants include:
1 Longspine Black Urchin
1 Baby Horseshoe Crab??
1 Coral Banded Shrimp
Numerous Snails and Hermits
1 False Percula
1 Valentini Puffer
About 22# of LR (I'm getting more)
Is it possible one of these guys ate my horseshoe crab (specifically the coral banded shrimp or the puffer)? <Not without any evidence... bits and pieces laying about.> My next questions involve my urchin, I noticed when I was doing my weekly water change that every time I put a little bit of water in, the Urchin would excrete this white 'goo' for lack of a better description.  Is this similar to what Sea Cucumbers do and is it harmful? <Coincidental, but likely a spawning event - urchins do this every so often. Not the same as cucumbers.> And lastly, will my urchin kill my live rock, only recently did he move from the glass to the rock. <No. Cheers, J -- >  

Question About Horseshoe Crab
I recently purchased a 1 inch horseshoe crab for my saltwater aquarium a week ago, and it died suddenly. I had a Damsel with it and  the damsel is doing  just fine. I read your article on horseshoe crabs and saw that you should feed horseshoe crabs blood worms ,mollusks etc. The lady at the pet store said that they eat fish food , and so that's what I fed it. Do you think that my horseshoe crab died because I was feeding it the wrong food? Thanks so much for helping.<I don't think it could of been the food you were feeding but it could be that you overfed.  You need the check your water parameters before you do anything else.  You can read more at www.wetwebmedia.com Cody>

Horseshoe crab Overview 4/14/03
Hi I was looking around wet web media and didn't see any articles on horse shoe crabs like what they eat and size so I was wondering if you could tell me or point me in a direction of where it would be on your web site thanks JM
<the following is a bit that Bob and I recently penned on this creature. Best regards, Anthony:
Caption for photo: "Horseshoe crabs are not true crabs at all, but actually much more-closely related to spiders. They are also inappropriate for mixed invertebrate aquariums for many reasons. These "crabs" need to be kept in large, specialized (non-reef) systems that are have great open surface area and sand of depth. Definitely not recommended for casual keeping in small home aquaria with coarse sand and dense rockwork. The most commonly available species, Limulus polyphemus commonly ranges from Nova Scotia down to the Gulf of Mexico and grows to 2' long X 1' wide (60 cm  X 30 cm). Several other species are seen in coastal waters from Japan to Indonesia, but do not appear in the US hobby."
Overview of Limulus polyphemus
By any definition, horseshoe crabs are ancient relics of the past. They have not changed much in the last several hundred million years dating back to the pre-Cambrian era (and are closely associated with their fossilized relatives, the Eurypterids). It is no wonder why they are described so often as "pre-historic". The design of their body has facilitated their long survival through the ages with its strategic and fully encompassing hard shell. Limulus are also extremely hardy in the present wild... enduring severe extremes of temperature and salinity. They are also said to be able to suffer seasonal famine and live without food for as much as a year! A year is also about how long it takes for these crabs to starve in mismatched marine aquariums. Too often, horseshoe crabs are placed in small aquaria with lots of live rock and not enough sand to burrow, forage and survive. Mind you that an abundance of live rock is very beneficial for reef aquariums. The problem is that these creatures, though, do not live on the reef proper. They do live near the reef, however, and will thank you very kindly if you provide a large open bed of deep fine sand for them to dig in. It takes perhaps 10 sq. ft per crab of more at >6"/15cm depth). It is interesting to note that horseshoe crabs may stay buried in the sand for days or even several weeks at a time. Let's be very clear that they live or die in captivity by the presence of deep fine sand and mud and the food they find within. We recommend using finely minced clams and clean Tubifex worms (live or thawed frozen) as part of the staple diet for this creature in captivity. Other ocean meats may be taken with equal enthusiasm. Be very mindful of the size and composition of food offered; Limulus have no jaws to chew or crush prey but instead process food with bristles at the base of their walking legs (yes... they must walk to feed, as the food is passed and mashed by these bristles). Although hardy and peaceful in their natural habitat, these "crabs" do not fare well in captivity outside of large, mature specialized aquaria. They tend to linger for some months in captivity, but again, do not survive past a few months with casual care.
Limulus are not true crabs at all, they are rather distant relatives of the spiders, scorpions and even the lowly ticks. Aspects of their phylogenetic relationships are suggestive when you observe their anatomy. The most obvious similarity is their prominent pair of compound eyes. In fact, in addition to the conspicuous pair of compound eyes, these crabs have a second pair of simple eyes on the front side plane of the body. A horseshoe crabs vision is not for feeding however, but for evading predation and finding mates. It is estimated that their range of sight is about 3' (~ 1 meter). Limulus also have 5 pairs of "walking" legs and two specialized pair for feeding and pushing sand, the forward pair on males being distinctly thicker and larger. Perhaps the most distinguishing part of these creatures is their telson (tail). This aspect of their anatomy performs like a rudder for balance and navigation as well as providing ever-important leverage to right themselves from a vulnerable overturned position. Its also quite a formidable weapon (although not its primary purpose) with spines and "timeliness" when thrust erect to ward off a would-be attacker. Despite the armor, horseshoe crabs are in fact rather peaceful creatures. They seem to be fairly indifferent to each other and anything that's not interested in eating them. They are somewhat generalized scavengers that consume many different things strongly preferring polychaete worms and mollusks in the sand. Their natural feeding habits keep them very active at night though in captivity they are willing to feed most anytime of the day if stimulated. This is a large part of the reason why they starve in most aquaria- few are placed into systems with aged, deep mature sand beds that have adequate populations of food organisms to sustain them. It is estimated that Limulus grows approximately 25% with each successive molt for roughly the first decade of life until they reach maturity. Molts occur every 7-10 months naturally.
Reproduction is a bit of a ritual during high tide (full and new moons) in the spring or early summer each year. Droves of Limulus migrate to the shoreline to spawn and lay staggering amounts of tiny green eggs. A large female may lay as many as 20,000 eggs which are deposited in a series of holes that she digs along the water line. Copulation is a bit of an interesting display. The males of this species (characteristically smaller than females by about 30%) grasp a hold of a female as she leaves the water to make this run. They are dragged along as the females climb up the shoreline and fertilize each batch of eggs as they are pulled across each pit dug by a female. Wave action covers over some of these nests but numerous Limulus eggs are contributed to the food web above and below the water (fish, birds, etc). In aquariums, many fish will prey on small and young horseshoe crabs. Their chitinous shells have not become sufficiently hardened and they will suffer from repetitive harassment of even curious fishes like large tangs and angels. It should be no surprise that triggers, puffers and eels will readily predate them. It is also quite unnatural for them to be kept with cnidarians and forced cohabitation will usually lead to Limulus dying in the tentacles of an anemone, or large polyped coral. Keeping these crabs in captivity also has very practical implications for their metabolism and increasing size. Before you purchase one, ask yourself if you have the means to keep them as an adult as 16"- 24" (40-60 cm) if and when they are ten years old? If you plan for a full healthy life and lifespan for this creature as you would for any other household pet like a dog or cat, you will quickly realize the very special needs of this fascinating "crab". Our purpose here is not to discourage the popular keeping of this marine creature, but to discourage the improper keeping of it. In a simple sandy lagoon or shoreline display, Limulus polyphemus are remarkably easy and entertaining to keep.
Horseshoe crabs- beyond aquaristics: Although Limulus polyphemus are still observed in great numbers, natural plights and human activities have impacted their once abundant populations. Some states in the US have established protected Limulus sanctuaries on assigned beaches. These agencies have sadly followed the lead of governing bodies before them forced to protect their natural resources like the Japanese with now endangered Limulus. The US Federal government has even imposed regulations on the bleeding of horseshoe crabs for improved survivability on catch and release. The unique blue blood from horseshoe crabs has been studied for about fifty years for its remarkable medical properties. Research has focused on anti-bacterial and anti-clotting aspects and the substance known to medicine as Limulus amoebocyte lysate (AKA- LAL). An injured crab uses this substance to quickly clot and disinfect a wound. Medical science uses it to verify that human drugs are bacteria-free and safe. Blood harvested for this research is said to fetch $10,000-15,000 per quart! Sounds to us like somebody needs to either discover how to synthesize it, or how to breed Limulus commercially. Horseshoe crabs have other economic and research values. Their eyes have been studied to enhance our understanding of how the human eye works. Chitin (chitosan) in their shells can be used to manufacture contact lenses and cosmetics and is also said to have nutritive value in homeopathic treatments. Commercially is has been used as a metal sponge in waste water treatment, and medically is can be used to make hypo-allergenic sutures for surgery. Numerous other uses are being researched from this unassuming yet valuable creature. Conservation starts at home as they say. As aquarists, please be mindful of your contribution to the use of this precious living resource. Good aquarium husbandry of this and any animal we keep serves the species through improved awareness and understanding.
Fenner and Calfo 2003

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 Crabs
Surprise surprise, false information from my LFS. So now I turn to people I can trust.
Hello Bob (or who ever may be filling in if unavailable).
Ok. I just purchased 2 horseshoe crabs for my tank. I have read through the information you have on your site and they really are some pretty cool creatures. First, I was told that these are reef safe - I haven't found anything that says they are not but just wanted to be sure.
<What sort of reef? Not tropical ones...>
Secondly I was misinformed about what they eat. Now I see that they eat worms and mollusks. Is there a certain kind of worm (and will they eat fireworms?). There are also 4 different classes of mollusks. Do they eat all of them or only certain ones?
<Many types of worms, smaller mollusks of all kinds>
Do you know of any kind of foods for them that one can easily purchase?
<I would search on the Internet here... these animals are used extensively in research... depending on your filtration, tolerance for different types of pollution of the rest of your livestock... you will find there are choices>
I have read in some of your Q&As that these are not a good purchase. 
<Yes, agreed>
Well, it's too late now and I want to make sure that they do well and don't starve to death. I am also trying to determine what one could do with them when they get to big. Maybe I could donate to a zoo or something like that.
<Or back to the shop whence they came?>
Oh, one last thing. About their growth, I know some marine life can grow large but don't due to the size of the tank. Are these like that or will they just keep growing?
<They generally don't live long in captive care, but can/do grow very large in the wild. Bob Fenner>
Thanks in advance, Steve

Horseshoe Crabs
Hey
I have a 120 gallon fish only saltwater aquarium. Just recently I purchased a horseshoe crab from my LFS. There it was walking around on the sand and acting fine. When I introduced it to my aquarium it went straight under the sand. He has only came out once at night that I have seen. I have had him for about 4 days now. Is that normal?
<Yes>
If not what should I do? Will he ever come out?
<From time to time, particularly when he has eaten everything in your sand bed and runs out of food.>
The other fish in my tank are a Small Volitans Lionfish and a Foxface. Thanks for all the help in advance.
<You are welcome. -Steven Pro>

Horseshoe Crab
Hello WWM crew, I wanted to see if you could help me out.
My girlfriend insisted on buying a horseshoe crab which has been living with us for about a month know but about 2 weeks ago we switched tanks from a 110 to a 180 gallon tank and as the 180 cycles with the Damsels we have the horseshoe crab in a 20 gallon tank with some of the old sand. My question is what do these guy's eat ? 
<hmmm...somewhat scavenging omnivores that favor clams and worms... do check out the following link: http://www.marinelab.sarasota.fl.us/WHORSESH.HTMon/>
Should I just drop some brine shrimp?
<frozen adult brine shrimp are a dreadful food. They are nutritively barren... essentially water in the shape of a shrimp. Your horseshoe crabs, fish, etc will "starve to death" (die of a deficiency) if brine shrimp make up any significant part of their diet>
I'm getting worried that he may be starving to death since he doesn't move as much as he use too.
<Agreed... they are very active at night and can starve in a matter of weeks without regular/daily feeding>
Thanks.
<best regards, Anthony>

Horseshoe Crabs
First off, great informative website! I have had a 3"-4" live sand bed now for a month in my 25tall tank(1year old) and EVERY hair of that dreaded hair algae has disappeared.
<Good for you. DSB are quite beneficial when properly constructed and maintained.>
I do weekly 5gal water changes which makes up mostly all of the attention I give my mini-reef other than feedings). I have 2 of each: cleaner, peppermint, camel shrimp, yellowtail damsel, green Chromis, and 1 rock blenny. I just added a horseshoe crab that's the size of a 50cent piece, was that dumb? I didn't find info on this site and I bought it cause it was pushing the sand around in its tank like it loved it.
<In general, not a good thing to buy something you admittedly know little about. The FAQ for these animals is here http://www.wetwebmedia.com/crustfaq.htm -Steven Pro>
Now in my deep sand it just buries itself and hardly ever comes out. Thanks for all your previous successful advice, Nelson

Horseshoe crab
Does a horseshoe crabs tail regenerate?
<Yes, with successive molts. Bob Fenner>

Horseshoe crab
Hi Anthony,
<cheers>
Sorry to bother you again. 
<no bother at all>
Do you know anything about horseshoe crabs? 
<yes... the husked shell of a large dead adult crab looks just like a Nazi helmet perched atop a man's head>
Is it usual for them to hide in the sand for periods of time? 
<perfectly natural for short periods>
Mine would buzz around the tank some of the time, 
<when you first got him (days) or are we talking months? Days is normal>
but has been in hiding for a day. I know they are night creatures,  is it possible that he comes out when I have gone to bed? 
<exactly>
Should I go looking for him, or leave well enough alone?
<if your temp is under 80F, leave well enough alone. They don't favor extended high temps, but they are very hardy and adaptable. They also prefer finer substrates (sugar sand)>
Thanks again, Kathy
<quite welcome>

Horseshoe crabs
Robert
I have recently acquired a horseshoe crab.  He tends to float upside down a couple times a week. I just tip him and he falls back down. Why does he do this or is this just a normal thing? 
<Likely the latter. Horseshoe crabs "do" seemingly strange behaviors... even when there is plenty of oxygen, an absence of noxious effects...>
This is the first time for a question to you but I have only been a member for 3 weeks. Thank you for your educated answer ahead of time.
<Thank you for your input my friend. Bob Fenner>
Kyle Rubarts

Horseshoe Crabs
Well, I wasn't expecting that one, but then again I went by Boo for 5 years in college, long story involving a late night of drinking and a young lady, now that I think about it, who reminds me of stomatopods...
<Boo? And a young lady... all sorts of images (non tasteful) are coming to mind...>
On another topic, I've seen several places offering horseshoe crabs as sand stirrers, from what I gather these are coming out of the Caribbean and Gulf of Mexico, do you have any idea as to how large these guys get?
<A couple of feet in length/diameter if they live... not good choices.>
I remember seeing some rather large ones (well over 12" across) when I was a kid and
we'd go to Assateague National Park. I'd certainly rather not put something that'll grow that large into the 300g I'm planning, it certainly wouldn't be fair to cramp it up that much. OTOH, if they only get around 3"-5", would they make a good sand stirrer?
<There are better choices... see the "Sand Stirrers" section on our site. Bob Fenner>

Horseshoe Crabs
Bob,
Thank you for responding to my last couple of e-mails. Your advice is greatly appreciated! I just added 5 horseshoe crabs in my 100 g. tank to help stir the substrate. Three of them disappeared into the sand as I thought they would but there a couple that keep flopping around and swimming in circles. They start to go under the sand and then they come right back out. Sometimes they end up on their back. They will turn themselves over after a while. It is tiring to watch...I feel like I need to help them out. It's like they don't know what they are doing. Is this normal? 
<Yes... normal... they even do this in the wild! Hard to understand how they've made it all these eons...>
Will they eventually get under the sand?
<Maybe... some stay on top... others perish. Bob Fenner>
Thanks so much for taking the time. Cathy M.