40g breeder on 30g regular stand?

your floor is going to get wet. a glass tank is supported only by the rim.
an acrylic tank has to have full bottom support. either way, you can't do
it.

is it a breeder or a long, while everything charlie said is true, breeder
tanks are generally better on interesting setups, if you browse the FW
setups you can find people putting there breeder tanks on very interesting
things, that i would never attempt with a normal display tank.