HCA: Hermit Crab Association

I wasn't able to reply to the thread where this question appeared as it's been locked but one of our newer members asked what to do if humidity became too high and was told there's no such thing as too humid for a hermit. Actually, besides the issues of mold, I've learned that it is possible for humidity to be too high for a crab. While hermits normally can handle high humidity, too high can make it difficult for the hermits too breathe and has the potential to cause gill infection. It can also throw off the delicate balance of shell water and lead to streaking.And in the same thread, "regular" thermometers should not be used in a hermit tank. Please get a dial or digital gauge and not one that contains mercury.

Thanks for posting this - I was going to reply on the original thread but couldn't think of a reason that it could be too humid, I just knew that it could.Dial/digital guages that aren't specifically meant for terrarium use are still OK though, right? Also, I was browsing around and was wondering what the difference between outdoor and indoor gauges is.Thanks!

Reptile gauges, and indoor/outdoor gauges are okay for use whether dials or digital. The ones you don't want are those that contain mercury (for obvious reasons), metal or the adhesive strips that are used on fish tanks.

The adhesives...do they contain something harmful?

They're not sensitive enough to accurately respond to air temp.

I remember reading that 100% Humidity isn't bad in short doses, considering it does rain. The problem is that its almost like drowning. Their gills depend on both humidity and air, so just as 0% humidity is too dry for them to live on, 100% is too wet for long periods of time.

Okay, now I am worried that I may be drowning them. Is 85 to 90 percent too high? I can lower it if it is a problem.

Ocean can you shoot for 80? I'd even go a little lower if it's the tank your newbie(s) are housed in.

also, it might be lower depending on where you have the gauge in the tank. When I had a waterfall at one end of my tank, it would be around 90-100 humidity at that end, and down to 70-80 at the opposite end.

No, its not the reading of my iso tank. That is around say, 75 percent give or take. As for the position of the main tank gages, I have my gage probes at around the middle of the tank and hanging at around half way from the bottom. Any lower and the crabbies think they are play things. I can lower it to about 80 maybe even 75 percent by turning on the heat lamp that'll bring the temp up to about 80 degrees. Its at about 70 to 75 degrees right now. That will make it ideal right?

So current humidity is 85/90 and temp is 70/75? The lower end of your temp is a bit out of range for them, s/b 72 minimum so you do need to bring it up a bit. Maybe turn the heat lamp on and crack the lid a bit so you're not boosting temp 10 degrees all in one whack.

Okay, after turning on the heat lamp last night and cracking the lid for a bit, temp is 85 degrees and humidity is 71-72 percent. Is that better?

I was wondering what do you do if you have extreme humidty differences on opposite sides of the tank. When I kept my gauge in the middle of the tank the humidity was perfect...or so I thought. I started moving the gauge around and found on the side of the tank with the heater the humidity ran around 60% and on the other side of the tank it was showing 90%-95% It is only perfect in the middle. So I started raising the humidity so that it stays around 75% on the side with the UTH. That is where the crabs tend to spend most of the time. That puts the humidity around 95% or more on the side without the UTH. What do I do in a case like this? Do I fix the high humidity or the low humidity? I remember we had a thread on this several months ago, but I don't remember ever coming up with a real solution. Please correct me if I am wrong.

You might find mold on the too high side but that's a different topic.A water dish situated near a heater could increase humidity as would a bubbler or DIY humidifier so if either of those are on the high end you could try moving them, also any water source such as a large dish placed near a heater would increase %. Try playing with placement of any water sources you might be using. To boost the low end you can add moss.