a light or uth would have to get pretty hot in order to melt a rubbermaid. The most I have ever seen was the rubbermaid buckle a bit under a heat lamp. All I will ever use is a rubbermaid enclosure. they are cheap and easy to build and heat, what more could you ask for? I have built several different setups. I used to have a large rubbermaid about the size of a 30 gallon long tank. Now I have 3 shorter versions in a rack. I have even built mouse houses out of rubbermaids. Like I said before....If I had fish, they would probably be in a rubbermaid. If you want to set one up and need some help let me know.