Is this a good one?

[Oliviet#1]

Please read the whole thing before answering.
Hi, I have a 20 gallon high tank and the backside is 24” by 16”. I am planning on having small micro or tiny hermit crabs so the substrate will be at least 6” tall. I need an under tank heater for (the back of) my tank. I saw that the brand hermit crab Association used for an UTH is too expensive. I found a brand called ipower on amazon that I can probably afford, and their biggest size is 8” by 18”. If I put that on the back and top of the tank and when it goes down, it will leave 1 inch of space above the substrate (unless I add another inch of substrate), and six inches of space to the left and right of the mat. Should I use that, and a 6” by 8” with it to make the whole length? (Btw the 8” by 18” is 24 watts, and the 6” by 8” is 8 watts and I saw they said they put some insulation inside the mat to keep heat in) if I add the 24 watt one with the 8 watt one, would it be too hot? How many degrees would it make the tank go up? (Ps our house is usually kept at 68-73,mainly low 70’s and was wondering if it would be too hot)

[mortemarts]

I wouldn’t recommend getting the heater to put on top of the tank. My reason being is that the hermit crabs could dry out not being able to escape the heater if needed. What I recommend is either getting a simple heating pad from Walmart of Walgreens. If you get a thermostat and keep an eye on it you could change temps whenever needed. I bought one of the UTH or something of that sort and it wasn’t cutting it since sometimes I just needed it to warm a little. But since your house is a good temp I would go for a low wattage just to warm, you don’t want to steam your crabs. Hermit Crabs prefer temps of 75-80 F.

[purplepincher]

you could put a cool side of the habitat.

[Hermiesguardian]

It won't be too hot. The 8 watt will probably not do much. I'm not familiar with the brand you mentioned. It might not be able to be insulated. If the crabs are too warm hanging out toward the back of the tank, they just move closer to the front. Do you have a thermometer/hygrometer? It's very important to have that. Digital is more acurate. You may find you even need a heater on the side too to keep it warm enough.

[Oliviet#1]

I wouldn’t recommend getting the heater to put on top of the tank. My reason being is that the hermit crabs could dry out not being able to escape the heater if needed. What I recommend is either getting a simple heating pad from Walmart of Walgreens. If you get a thermostat and keep an eye on it you could change temps whenever needed. I bought one of the UTH or something of that sort and it wasn’t cutting it since sometimes I just needed it to warm a little. But since your house is a good temp I would go for a low wattage just to warm, you don’t want to steam your crabs. Hermit Crabs prefer temps of 75-80 F.

Thanks! I meant to say the back of the tank though lol