Im just starting a new build for my leucs (exo terra 90x45x45) and i have an egg crate false bottom, but i am keeping a small corner open for a water area which will hopefully be used to drop tads into sometime, but my question is how do i stop the water from just going through the mesh of the false bottom and flooding the bottom of the tank.

I was thinking of the expanding foam, but i can only get white foam in the UK and thought it'd look a mess?Any ideas?