I have a small colony of dubia roaches. I have 3 geckos and 1 Cuban false chameleon, and the Cuban is the only one that eats the roaches on a regular basis. So I don't go through a ton of them, maybe 4-5 per week. My problem is that I have too many adults that are too large, and they are not reproducing well, as I think my temps are a bit too cool (70 at night, 73-76 daytime). I have them in a Rubbermaid tub inside of a larger Sterilite tub to avoid escapees. I am wondering if I can put a heat mat under the inner container to make it warmer, without having to hang a heat lamp. I know the mats are usually used on glass tanks. Would it melt the plastic? I know I would have to raise the inner tub a bit for some circulation, that's not a problem, but could I attach a mat to the underside of the inner tank?