why foam?

[kien]

It is a good idea, especially on larger tanks and/or tanks that don't have a trim on them (bare glass on stand surface). If you happen to have something like a speck of sand, dirt, debris under the glass or even just unevenness of the surface that you are putting your tank on that is a single pressure point that could stress that bottom pane of glass. Over time it could cause issues. The foam at the bottom helps to cushion and even things out under the tank.