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 -- >