either tile or something that could be replaced if neccessary. Tile would be optimum. If you do wood floors, it actually needs to be a gluless floor so engineered, tongue and groove, or laminate are your best choices. Any wood product or wood byproduct flooring that gets wet constantly will need to be replaced eventually. I did a laminate plank flooring, and bought an extra box for when we move to replace around the tank. You do need to make sure it can handle the weight and do not pick anything soft or medium hardness because it will dent. ALSO, if you choose a prefinished floor, make sure you get it with a uv protection coat or put UV tint on your windows because alot of the pre-finished will turn colors ie get darker in a sunny room (but not where a rug or your tank is)