HCA: Hermit Crab Association

So, we came home from a beach vacation with three boardwalk hermit crabs, and set about reading and learning all we could to create a nice crabitat for them. We have a 10-gal aquarium with mesh screen lid, filled with 6 inches of 1:5 Eco Earth and general purpose sand, and all the usual accessories. We are using some large clam shells for fresh drinking water and the salt water bath.

We don't see much of our crabs, as they're spending our waking hours buried in the sand, but we do see two of the three coming out for food at night. They must be using the salt bath, as we're always finding fresh dirt (poop or sand/EE mix?) in the salt bath shell.

My question is about changing out their water, both fresh and salt. I've been pulling the shells out and dumping the old water down the drain, and filling with new water (both fresh and salt) every 2 days, but wondering if it's really necessary. I don't like the sand I'm putting down my drain, as a result of this process, and wondering if most just top off their water rather than dumping and filling fresh several times per week.


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Yes, the water needs changed frequently, especially if they're dragging substrate/poop in - ammonia levels can build up quickly and it's extremely harmful. Can you dump the shells outside instead of down the sink?

Also, I'd suggest different water dishes. The crabs need to be able to submerge in both types of water to clean out their shells and replenish their shell water, and I'm not sure clam shells are going to be deep enough for them to do so You can use plastic containers from the dollar store as a cheap alternative.

Interesting. Most of the guides I read and watched suggested keeping the water shallow and providing a ramp out, to avoid drowning, so I've been doing just that!


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Nope, the deeper the better! They do need an easy way out, which can be accomplished with a fake plant, a piece of decor, needlepoint canvas, etc. Quite a few people have pools deep enough for their crabs to go underwater fully, but the minimum depth needs to be enough for the largest crab to easily get water into his shell.

Okay... so how deep for a "medium" crab? Are we talking a full shell diameter depth? Half shell depth?

You can use dollar store or cheap disposable tupperware style dishes. We recommend that the crab be able to submerge. As long as they have a way out, they won't drown. Here is a pic of my pools, made with inexpensive 2.5 quart plastic containers:


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Are the shells in the pools to help aid smaller guys, decoration only or...? I'll be setting up my pools tomorrow hopefully so just curious


Zoo mom of 3 cats, a dog, a fish and 6 crabs

To weight down the craft mesh and offer additional climbing. However I have crabs swap in the water quite often so they have actually become secondary shell shops as well.

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Ok cool...that's good to know they'll swap while swimming.


Zoo mom of 3 cats, a dog, a fish and 6 crabs

When you say "frequently", do you mean daily? Every two days? Once a month?

Ideally every day, same as a dog or cat. Immediately if they track a lot of organic substrate or any food in, since it will start to rot. If they keep it fairly clean then every three or four days at the most won't hurt them.

Cool. We've been doing maybe 4x per week, so I guess we're in good shape. Thanks!


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I wanted to take a second and add to what Wode said. After seeing photos of your tat, those tiny shallow dishes need to be changed daily. If you have pools deep enough for them to submerge (recommended), you can get away with every few days.

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Okay. Hunting for a cosmetically acceptable (ie not Tupperware) water dish option now. Want these little guys to be healthy and clean.


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