Our first SW tank - 180 gal build

[ensquire]

This is the plywood the Grizz is referring to. This should all be one solid piece of Plywood not osb of mdf. If this gets any moisture at all it will expand and possibly crack your tank. Also there should be a half inch piece of rigid styrofoam between the plywood and tank.
I agree that the platform it sits on looks well built and solid and with a little silicone and sealer will be very moisture resistant.