Tank And Cabinet

It depends on the construction of the tank. Broadly speaking there are 2 types of tank.

1) Flat bottomed. The bottom of the tank is a sheet of glass and nothing protrudes below the base. This type needs something between the tank and the cabinet - a layer of polystyrene, a purpose made base mat etc. The danger is that a defect in the cabinet or even a grain of sand could stress the base glass so much that it cracks.

2) Floating base. This type of tank has a rim of glass, usually plastic covered, which extends the sides down below the bottom glass. There is a hollow between the bottom glass and the cupboard. This type should never have anything between the cabinet and tank. With some makes, putting something there invalidates the warranty.