what size UTH?

[golfinfool]

I have a tank that is 18 x 18 x 12" high. We currently have 3 small crabs and 2 medium sized crabs. We have had the medium crabs for about 3 months now and just picked up the smaller ones. My tank temp is usually around 72 degrees and the humidity is around 85%. What size heater should I use and do I just mount it to the back of the tank. The back wall of the tank is 18 wide and 12 high, there is currently around 5-6 inches of substrate (play sand). I was looking at the Ultratherm 11 x 17 but wasnt sure if that was too big. Thanks for all your help!!!

[CallaLily]

I think the 11 x 17 will be fine. It's usually recommended for it to be all or mostly above your substrate line (just because it is drying to the substrate), but that's difficult to do with smaller tanks and still get the heat boost you need. Just keep a close eye on your sub to make sure it doesn't dry out.

[Kleinerhejhog]

Is it just me, or does 18 x 18 x 12 sound small for five crabs?

[wodesorel]

Is it just me, or does 18 x 18 x 12 sound small for five crabs?

If they're really tiny it should be okay, but as they grow it's likely they're going to run into some serious trouble when molting. The biggest threat to an established crab is another crab come molting time. Overcrowding isn't just a quality of life thing with hermits, it's a major issue since they are naturally cannibalistic. Making sure there is enough space so they can molt without being discovered is key!