I have not taken him out to measure. Just eyeballing, 15-16". Eats pellets, shrimp, tilapia, frozen food. Also, loves to clean off all the algae on tank.
Tank is only a 120 gallon. I would say at least 180 gallon or bigger would be ideal. He doesn't hide a lot, not shy at all, loves to clean algae and great personality. I only rent right now, so limited with tank size.