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FAQs about Horseshoe Crabs, Behavior

Related FAQs: Horseshoe Crabs 1Horseshoe Crabs 2, & FAQs on: Horseshoe Crab ID, Horseshoe Crab Compatibility, Horseshoe Crab Selection, Horseshoe Crab Systems, Horseshoe Crab Feeding, 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),

Live most of the time under the sand...

Horseshoe crab molting     4/5/17
To whom it may concern,
<Sara>
I'm a naturalist and we have a lot of aquariums at my nature center. We've had a resident horseshoe crab (about 5-6" diameter) for some time, but his last molt was unsuccessful and it seems to be in poor health now. It's
limbs an carapace are deformed.
<Mmm; there are a few general "causes" for such: A lack of iodide-ate, imbalance/deficiency in alkaline earth materials (mostly Calcium; to a lesser degree Magnesium), "poor" water quality outright (e.g. too much
organic content); and lack of nutrition. You should look at all these possibilities>
It's been flipping itself upside down repeatedly today with no success in righting itself (I've tried righting it several times by hand). It still eats fine and the water levels are all normal;
<.... data please; not impressions>
everything else in the tank is in fine health (urchins, another horseshoe, etc.).
<Ahh; a good clue>
Is there anything that can be done to help ensure a successful molt?
<The above considerations. Do you have test gear for water parameters? What are you feeding, using for supplements?>
Based on my observations, I think it should've molted again by now but it just hasn't.
Thanks!
Sara Yinger
<Let's keep chatting till this is solved. Bob Fenner>

Horseshoe Crab questions       4/6/15
Hello guys, im Patrik, I have a 40B <G?> saltwater tank that's been running for a year and a half with a 10 refugium, all levels as low as stability allows salinity 1.026. The 40 has my salt cat and snowflake eel and the fuge is for my nems crabs and shrimp, well in my travels I was given a horseshoe crab about the size of a quarter in a gallon pickle jar. Its molted once in the 8 months I've had it and is now 2 1/2 inches. He eats shrimp pellets and crab meat and any krill that are left from the nems and seems pretty happy never had a single issue with him. In the past month I've noticed he likes to come out around noon and midnight, so lights on and off, and lay upside down on the sand in one particular corner with low flow. Im worried because it is strange but he stays still if I try to flip him
<Don't do this>
over like doesn't react at all for a minute, then even if im still messing with him he starts wiggling his legs so maybe sleeping or something and I have a 4' by 4' pool for him to grow into one day so id like him to live as long as possible.
Any and all help is very much appreciated, thank you.
<See (i.e. READ) on WWM re these animals.... You likely have a cold water (temperate) species (there are tropical ones though)... NOT suitable for a tropical setting. 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.

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 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>

- 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 -- >  



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