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FAQs about Horseshoe Crabs, Foods/Feeding/Nutrition

Related FAQs: Horseshoe Crabs 1Horseshoe Crabs 2, & FAQs on: Horseshoe Crab ID, Horseshoe Crab Behavior, Horseshoe Crab Compatibility, Horseshoe Crab Selection, Horseshoe Crab Systems, Horseshoe Crab Disease, Horseshoe Crab Reproduction, & Crustaceans 1, Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating Shrimp

Related Articles: Horseshoe Crabs: Latter Day Trilobites for Some Systems & CrustaceansMicro-Crustaceans, Amphipods, Copepods, Mysids, Isopods, Shrimps, Coral Banded Shrimp, Cleaner ShrimpP. holthuisi Pix, Mantis "Shrimp", Lobsters, Slipper Lobsters, Hermit Crabs, Squat Lobsters, Crabs, Arthropods, Pycnogonids (Sea Spiders),

In the wild they live on interstitial fauna... mainly worms, crustaceans, molluscs twixt the sand/silt/gravel grains... in captivity? The same, plus maybe foods offered under their "shells"

horseshoe crab, fdg., sys. gen.     2/5/13
I have been reading and researching your site on horse shoe crabs and had a few things i wanted to discus with you. I have a little horse shoe crab
<The eastern seaboard species I'll assume>
 in a 10gal salt water tank. he was about 2 inch's when i got him, and now he is about 3 to 3 and a half. I have had him in the tank for about a year at this point and he has not starved to death. My salinity is between 1.024 and 1.025, ammonia and nitrites are both at 0 or close to, my nitrates are kinda hi, but they have always been high in my tank and despite anything i do i cannot get it to come back down.
<Not so important w/ these relic species>
 So far the only adverse affects to the high nitrates is a bit more red hair algae than i would like (the snails keep in under control for the most part) and my plant seems to like it as well (not sure what kind, obviously saltwater plant, its kind of  like a vine and it raises little stocks that disk shaped "leafs" grow on).
There is a very healthy bristle worm population in the tank as well as he seems to enjoy algae wafers made for Plecos and other such fish as well as high protein wafers made for catfish and other bottom feeders. He does seem to come out and eat with everything else in the tank and chasses around bits of flake food but his favorite seems to be Hikari Multi-Vitamin Enriched Brine shrimp. As for the trace elements in the tank, i use Kent Marine Nano Reef two part supplement. It is recommended for use every day, but i don't use it that way, i add that about one a week, sometimes twice if I'm feeling spunky. Tank mates include a mis-bar clown fish, a blue-green Chromis, peppermint shrimp, two Astrea snails, two dwarf blue legged hermit crabs and a group of about 9 Zoas. There was at one time a mini brittle star that came in with the Zoas, but i have not seen hide nor hair of that little guy in over 7 months so i think he died and got ate, or just got ate. There was a narsis snail and another Astrea snail, but the hermits wanted bigger shells and they didn't like any of the upgrades that i provided for them.
There is about 6 to 7 pounds of live rock, and about 20 pounds of live sand to make a sand bed of about 3 inches deep. The sand is larger grain, not fine grain, but he really does not seem to mind. I really love this little guy, he is awesome and by far the best purchase i have made. Hours of entertainment watching him walk around the sand eating, and swimming (not very well) upside down around the tank. And yes i know how big they get, i have already located tanks that he can be transferred to as he grows, including a fine grain, 6 inch deep sand bed in a 180gal tank with plenty of Spionid worms for him to break up and eat. I guess what i want to know is is there anything else i need to be doing for this little guy?
<Doesn't appear to be; no>
As i have stated he has had no problems so far, but i want to keep him this way. I have not found anything on your site with anything i really need to change so I'm just double checking that i have not over looked anything. its hard to know what your looking for when there is no problem to solve. thank you for your time and for your help! i greatly appreciate it.
<Well, the other life, fishes and invertebrates would likely appreciate lower nitrate... not easily done in the size/type setting w/ the horseshoe... All will appreciated the larger habitat. Bob Fenner>
Re: horseshoe crab    2/6/13

Thank you for the quick reply! any quick tips for lowering nitrates in a small tank other than moving them to a big tank? i would like everything to be as happy in the tank as can be.
<Read here: http://www.wetwebmedia.com/nitratesmar.htm
and the linked files above. The mechanisms, techniques of nitrate control are the same regardless of size of the system. BobF>
Re: horseshoe crab    2/6/13

thank you very much!
<Ah, welcome. B>

Atlantic Horseshoe Crab/Feeding/Systems 4/19/10
I have recently bought a Atlantic Horseshoe Crab and I am not sure how often to feed him. I have 4 foot tank which is 350 lt.
In my tank I have clown fish, damsels, Chromis and 2 Chocolate Chip Star fish.
<<This animal can't live here with these fishes... is NOT tropical... RMF>>
My star fish eat white bait and the other day I put half of one in the tank for the star fish and the crab eat it instead is it ok for the crab to eat that.
<Yes, will eat most anything.>
Please let me know how often to feed him I don't want to starve him but I also don't want to over feed him.
<This species is principally a sand-sifting filter feeder, though there are other horseshoe crabs that are more predatory.
Most Horseshoe crabs are short lived due to lack of nutrients, inappropriate systems. Do read FAQ's here.
Many thanks
<You're welcome. James (Salty Dog)>

Re: Horseshoe crab arriving today  11/22/09
Hi Neale,
He is eating well. One question -- you mentioned I should put him on his back and put the food into his "claws", then let him eat for an hour or until he defecates and then return him to his tank.
Do I leave him on his back while he eats or do I just get him "started" that way then turn him right side up so he can move around while he finishes eating?
<Until he gets started. The idea is to present food to the animal, so you know what and how much it is eating. Once its eating, turn the thing the right way up and leave him to it.>
Thanks again,
<Cheers, Neale.>

Horseshoe Crab/Feeding 4/22/08 Hello Guys, <Hello Scott> I had originally composed an email to y'all with a cleverly-worded story of how I came to own this guy. It was a real gem probably would have ended up on your refrigerator door. But let me cut to the chase. <Mmm, reminds me of a George Strait tune.> I now own a 1-inch diameter Horseshoe Crab. I want it to live long enough for me to be forced to donate it to the touch-tank at my LFS. He is in a 125-gallon tank with 6 ft x 1.5 ft floor space. Well over half of it is wide-open sand. The substrate is 350 lbs. of sugar-sized silica sand (Quikrete Fine No. 1961) five inches deep. The rocks are resting on the aquarium bottom, not on the sand. At night, when they come out, the visible Amphipod population density is about one per square inch on the rocks and shells of the large (two-to-three-inch diameter) Thin Stripe and Elegant Hermit Crabs. On the open sand, it is much less, except where there is something of interest to them. From one of your FAQ's: "When I introduced it [newly purchased horseshoe crab] 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. " QUESTION: Arthropods don't get skinny. Is this how I can tell if he is starving i.e., if I see him a lot? What other signs are there? <Well, the crab may appear more often on the surface of the sand in search of food, but is best to offer meaty items such as squid, clams, etc. about three times per week. Not too much danger of overfeeding these guys as they can grow close to two feet in length. All that is necessary is to bury the food in the sand shortly before the lights go off, they will find it.> Thanks for a great site! <You're welcome. James (Salty Dog)> Scott

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 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  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.

Feeding a Horseshoe Crab - 03/31/07 Hello guys! <<Good morning!>> I love your site, thanks in advance for the help here. <<Hope it proves useful>> I recently purchased a horseshoe crab for my tank. <<Mmm...and likely Limulus polyphemus...an Atlantic species>> I have fine sand, fairly deep (3-4 inches), a lot of room for him (75 gallons with little live rock), but I am worried about feeding him. <<75g is not enough room for a mature L. polyphemus...can grow to 12" in diameter>> I read that you are supposed to feed him blood worms/clams/mollusks. <<You can, yes...and a clam "is" a mollusk...as are mussels, oysters, snails, octopi, etc.>> I have blood worms, but I don't understand exactly how him to eat them.  Should I bury them in the sand so when he runs over them he munches them? <<I wouldn't>> Then I am worried that my cleaner shrimp would find it first.  I have also heard about sticking it under his shell.  Do I just grab him by the sides and put the food underneath him? <<Though quite hardy, I wouldn't advise subjecting it to this stressful activity on a continuing basis>> Also where can I buy mollusks?  I'm not really sure what they look like. <<Oh but you do! (see here: http://www.google.com/search?sourceid=navclient&aq=t&ie=UTF-8&rls=WZPA,WZPA:2007-07,WZPA:en&q=mollusks+definition)  Go to your local grocer and pick up some fresh clams/oysters/mussels from the seafood section.  place one of these on the substrate near the horseshoe crab...you can even help it out a bit if you wish by prying the shell open beforehand but this shouldn't be necessary...and as an occasional treat you can also present it with worms/Nightcrawlers from the garden.  And do be sure to remove any uneaten foodstuffs>> Thanks! <<Regards, EricR>>

How to Feed My Horseshoe Crab - 4/8/07 About 2 weeks ago I recently purchased a horseshoe crab, that is 1" in size. <Fascinating creatures but have specialized needs.> He only came out at night and not every night until yesterday, when it came out during the day. I wondered if it was hungry, and I read that horseshoe crabs eats worms and mollusks. I went to a seafood store and got a fresh clam. I put the clam in the tank, and the clam is alive. The clam is bigger than the horseshoe crab. The clam is about 2" big. The horseshoe crab has been running around the tank during daylight for 2 days now, burying itself at times. It has bumped into the clam a few times, and it has not seemed interested in it. Is the clam too big? <Yes> Is there a method to get the horseshoe crab to eat it? Do I need to open the clam? <I would instead offer the clam finely chopped, or perhaps mysis, clean blood or Tubifex worms. Please read the FAQ at this link: http://www.wetwebmedia.com/horseshoecrabfaqs.htm . As mentioned, these creatures have specialized needs, so please be sure you can provide them.> Any response will be appreciated. Thank you so much and have a happy Easter. Christian <You're very welcome and the same to you! -Lynn>

Horseshoe Crab: Feeding Frequency -12/17/2007 Hey Guys, Quick question, I have a 2 inch horseshoe crab. How often do you think I should directly feed him with meaty foods (ex: krill, Mysis, carnivore preparations)? Thanks!!! <Hmmm... how often does one feed a giant prehistoric predatory marine arthropod? Good question. I presume it will feed as it wishes (as much as it can find - both on the food you try to give it and on your benthic critter populations) despite whatever schedule you try to put it on. In any case, what will you do with this beautiful creature once it's the size of a small cat? Best,
Sara M.>

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