PNWaquarist
Aquarium Advice Addict
Not unless you are using an undergravel filter. Most of the bacteria will be in the filter. If your tank is well established, it will also be on every other surface of the tank.
Are undergravel filters even compatible with sand? I haven't used an UG filter silce the 1980s, and the plates on that one definitely would not have worked with sand. Not sure if the technology has changed much since then.