HCA: Hermit Crab Association

I'm working on setting up a tank and the humidity is too high at 85-99% and I took the lid off the tank and left it off all day and it still isn't lowering any I don't have anything in the tank other than 5 inches of eco earth a small amount of moss and a coconut shell (not on top of the moss) so I was hoping that maybe one of you may be able to help. if it is of any use I use brick eco earth.

thank you

You may eventually get a little bit of mold, but those humidity levels will not harm your hermit crabs.

It seems weird that it would not go down after removing the lid. Moss and coconut fiber can raise humidity, but this seems extreme. What are you using for a hygrometer, and has it been calibrated?


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I would also consider whether the hygrometer is accurate - I doubt your house is that humid!

I'm using an acurite digital hydrometer and thermometer

There is no such thing as humidity too high. Just keep an eye out for oversaturated substrate and a lot of mold.

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Anyways, here’s the link to hygrometer calibration.

http://www.hermitcrabassociation.com/ph ... hp?t=92540

Even Acurites need to be checked once in a while. If you haven’t, you may want to do so.


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My humidity stays at 99% with no issues.

Edit: btw, the HCA recommends your substrate be a minimum of 6” or three times the height of your largest crab. Whichever is deeper wins.


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We currently have 4 gauges in our 75 gallon, left, right, dead center, and center front. They all read slightly different, 89, 93, 85, and 99. I believe the one digital isn't working properly because it always reads 99. Possibly a low battery? I believe the others are in the ballpark since they are all at different heights. I like having a few in the tank so if I get a wonky reading I can rule it it out with the other gauges.