when you get your plywood get some birch ply the kind with no voids in it. they can cave in and there is a lot less sanding with the better ply i used a two part epoxy paint the kind they paint the inside of water tanks. and then i put in a 65mil pond liner to keep things from cutting in to the paint and the paint was gray so the black looks better http://www.garf.org/140.gallon.html http://www.thekrib.com/TankHardware/wood-tank.html#0