HCA: Hermit Crab Association

I am a first time Hermit crab mom, I have a 55 gal. tank with 2 heater mats under each side of the tank with the center being a "cool" area for the crabs to regulate their body temperature. I Use Eco Earth that is about 7 inches deep and gradually slopes down to about 4 inches at the other end of the tank. When I set up the tank, before I even considered getting the Crabs I set up the heating mats, soaked the Eco Earth logs in non chlorinated water, Squeezed out the excess water from the sub straight, and use a plexi-glass Top With 2 lights. The relative humidity is always between 75 to 90%
always without me doing anything to maintain it and it usually has water dripping down the glass inside. I have 7 crabs and I have had them for 2 months. Is this to much humidity? I have other questions but lets start there. Thanks

From what I understand, I do not think it can be too high to be harmful for the crabs.

Somethings to keep in mind that I have read is that high humidity will increase mold, but that it is not bad for the crabs, just might mess with the human allergies.

Some people keep their humidity at 99%. There are two possible problems you may run into and will need to keep an eye on.

With a higher humidity the condensation can keep building up on the glass and eventually pooling at the bottom of the tank. It can be dangerous if you have crabs down molting.

The high humidity can also cause mold inside the tank. I noticed mold really takes off in straight Eco Earth with pieces of food the crabs drag around.

Aside from that high humidity is harmless to the crabs.


http://www.hermitcrabassociation.com/ph ... 26&t=92544

Thank you so much for the help! I have been getting white mold and I scoop it up off the echo earth every time I see it.

I just wanted to clarify something. Are your heat mats actually under the tank? That isn't where they go for hermit crabs. It can cook them that way. They go on the outside of the glass, on the back or sides.
A slope is nice in the tank but the lowest side still has to be a minimum of 6 inches or 3x the height of your largest crab. Whichever is deeper.

Hermiesguardian wrote: ↑

Tue Mar 12, 2019 5:02 pm

I just wanted to clarify something. Are your heat mats actually under the tank? That isn't where they go for hermit crabs. It can cook them that way. They go on the outside of the glass, on the back or sides.
A slope is nice in the tank but the lowest side still has to be a minimum of 6 inches or 3x the height of your largest crab. Whichever is deeper.

I was just wondering, is it ok to put the heater under the tank if the crabs aren't molting or buried?

scuttlecrusty22 wrote: ↑

Wed Mar 13, 2019 11:49 am

I was just wondering, is it ok to put the heater under the tank if the crabs aren't molting or buried?

No. Because you never know when they'll go down. And you can't keep moving the tank because you can collapse tunnels and caves. It's the air you need to heat. Putting the heaters under the tank is for reptiles. Also with the amount of substrate we use it's a fire hazzard. If you haven't moved the heating pads yet you need to do so.

It is best to keep the heaters on the back or sides of the tank. You want to keep the air warm and humid similar to the tropics. Having the heater on the bottom of the tank will slowly dry the substrate eventually lowering the humidity.

Some crabbers will use a heater as close to the top of the substrate to the top of the tank. Others cover the entire back of the tank with the heater. Either of those are perfectly fine.

Hermiesguardian wrote: ↑

Wed Mar 13, 2019 1:36 pm

No. Because you never know when they'll go down. And you can't keep moving the tank because you can collapse tunnels and caves. It's the air you need to heat. Putting the heaters under the tank is for reptiles. Also with the amount of substrate we use it's a fire hazzard. If you haven't moved the heating pads yet you need to do so.

I don't have a under tank heater I was just asking but thanks anyway

You will see all the flat 'pad' type of heaters, called 'under tank heaters' or UTH, even though we put them on the back or sides. Zoo Med, Ultra Therm, etc. I think you do have one, even though it technically isn't going under the tank, LOL!

Undertank heaters are most commonly used for reptile such as snakes and lizard enclosures. Since reptiles can only regulate their body temperature by moving between warm to cooler places these heaters are always recommended to be placed under the tank by the manufacturer. They only need a "spot"in the tank to get warm. Also ZooMeds calls out tank sizes on their heaters for the same type of use.

With hermit crabs it is a little different. You want to be able to heat the entire air space of the tank so everything mimics tropical conditions. That's why we place the heaters on the back and sometimes on the side of the tank too. If you get a heater that is too small you may not be able to get your temperature high enough. Think of a single candle trying to heat a living room compared to a fireplace.

If the heater is placed under the tank the deep substrate will not let heat to escape properly and possibly overheat the heating pad or worst case scenario crack the glass of the tank. It can also dry out the substrate from the bottom up and possibly bake crabs or collapse tunnel of molters.