HCA: Hermit Crab Association

It’s been since September since I have changed my substrate. I’ve noticed that it seems very saturated now and water is pooling in the holes the crabs have dug. I don’t over mist. In fact I may only mist every other week. Maybe the humidity is too high. The hygrometer reads 99. Should I consider doing a full tank cleaning/substrate change?


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Can you add mire sand? Or ee? You may have to remove the crabs. I'm sure someone else with more experience will advise.

I had that problem. I removed 3/4 of my muddy substrate and added dry ee. I mixed it up with the muddy stuff in the tank and the problem was solved. I saved my muddy substrate in a bucket to dry out and added it weeks later.

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Just be careful of molting crabs that may be down

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That’s a great idea! I have my 55 gallon I’d like to set up and now seems to be the perfect timing for it. I just need to have my wife decide on a stand for the tank.


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I forgot to mention, I tilted my tank for a few hours to let the water drain to one side. Then I scooped out the mud. I scooped out as much as I could.

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Xenocrab wrote:I forgot to mention, I tilted my tank for a few hours to let the water drain to one side. Then I scooped out the mud. I scooped out as much as I could.

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Great advice! Thanks!


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Watch to make sure the substrate at the bottom doesn't start smelling. Anytime substrate gets oversaturated, there is a risk for a bacterial bloom. Draining it won't have dried it enough to prevent it. It doesn't always happen, but if it does make sure to throw away any spots that are affected. Crabs should also not be allowed to molt in oversaturated substrate because of the bacterial risks.

Does having substrate mixed with saltwater compared to fresh water lower the chances of having a bacterial bloom? I would think the salt would lower the chances of having bacteria grow.

I'm not sure how much of an effect, as the anaerobic bacteria that grow in oversaturated de-oxygenated areas occur in both fresh and salt conditions. Using salt helps with mold and mildew growth though.

I have always mixed my substrate with marine saltwater - and I have never had any issues, but then again, I don't mist/spray my tanks.

I think the misting and not misting shows how much conditions can change depending on where you live.

I'm sure with Stacy living in Florida temperatures generally will fluctuate maybe 15-20 degrees between winter and summer, if that. So heating a house to raise the temperature from say 65 to 72 is minimal at zapping the "natural" humidity from the air. I'm sure her general crab care stays pretty much the same year round, aside from when she gets bombarded with zoea.

With Xeno, myself, and Lee being in Pennsylvania and only 30 minutes or so apart its safe to say we all have the basic winter tank issue with humidity. Due to the fluctuation of temperatures between summer and winter of 50+ degrees we need to change our care based on the season. Xeno and I run insulated ultratherms on the side and rear of all our tanks in the winter to maintain a temperatures above 80 degrees. Cold temperatures outside of freezing and below takes more to keep our houses at a comfortable level forcing us to use more heating for our homes. For keeping a comfortable temperature in our homes we sacrifice "natural" humidity levels indoors. Eventually leading to sucking the humidity from our crabitats no matter what we do to keep them normal. Moss pits, glass tops and bubblers help to a point but we all still need to fall back to misting daily or every other day to keep a steady humidity.

Come summer I can unplug the side Ultratherm for additional heat and fall back to occasional misting to keep the moss from drying out. The crabitats definitely take more work to maintain levels in the winter for us compared to summer.

In the winter I always get cracked and bloody knuckles and sore throats from the dry air. usually running a humidifier at night helps my sore throats and lotion helps my hands. Since we are expecting a snow storm this afternoon through tomorrow afternoon I'm going to try an experiment with my indoor humidifier to see how running that in the same roof affects the crabitat. It may save a lot of headaches for us to run a humidifier in the room where the crabs are rather than misting non stop and potentially causing flooding and bacterial blooms.

Yes, and this past weekend was frigid! Temps around 0°F.

I’m working on getting stuff around for my new tank. I’ll probably get to actually setting it up within the next month. I’m getting very anxious to move them into their new home!


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As someone who ended up dealing with a bacterial bloom last year - I second the statement that mixing your substrate with fresh or saltwater does not seem to have an effect. My main issue was my Ultratherm getting too warm and drying the air out, (which surprised me) I would mist to get it back up. Little did I know that under the 12" of substrate I have that something nasty was occurring! I now have a thermostat to help me keep my temps at a reasonable level.

PinchersAndShells wrote:As someone who ended up dealing with a bacterial bloom last year - I second the statement that mixing your substrate with fresh or saltwater does not seem to have an effect. My main issue was my Ultratherm getting too warm and drying the air out, (which surprised me) I would mist to get it back up. Little did I know that under the 12" of substrate I have that something nasty was occurring! I now have a thermostat to help me keep my temps at a reasonable level.

Thanks for responding with your experience! I will be moving to a bigger tank over the next month so I’ll get to see if anything funky is going on underneath.


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