As a tile contractor for the last 20 years, I would say that you're fine. I've never seen a tank crack a floor. We have done some commercial/factory work where forklifts, vehicles, etc are driven over it and have never seen a hint of a problem where load was the issue.
Now - regardless, I would recommend that you use porcelain over a ceramic material as it is way stronger and is about as bulletproof as flooring can be. I recently tiled the bottom story of my house and used a self leveling product in the room where the tank was going. I've had up to a 180 gal tank in there.
Now - regardless, I would recommend that you use porcelain over a ceramic material as it is way stronger and is about as bulletproof as flooring can be. I recently tiled the bottom story of my house and used a self leveling product in the room where the tank was going. I've had up to a 180 gal tank in there.

