Under tank padding

I'd say that since most stands for large tanks are open, you only need to worry about the frame, and that's rather sturdy.

It's not going to hurt anything to use foam, but it's not really required either on a tank like that.

I do, but many of my stands are DIY, and lets just say my carpentry skills are not up to building a piano.

I have one under my tank. Just go to home depot or a similar store and buy one of their big sheets in the insulation section.