HCA: Hermit Crab Association

Should I place my UTH along the whole back of my tank? It measures 36" long. It is 6" tall to avoid the substrate. Don't my crabs need a cool off zone?

You can go ahead and place the mat on the entire back of the tank. Crabs are kind of like fish when it comes to temperature. Just like tropical fish like all of the water to be warm, the crabbies like their entire enclosure to be nice and warm.

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They'll be fine. The "cool off" spot is at the front of the tank. You can also set it on a thermostat or timer if you're worried.