I currently have a clownfish that rarely ventures more than an inch off of the glass of the tank, he seems to be doing laps around the tank! I’ve had him for about 3 weeks now and he’s still small only around an inch. I think it might be a flow problem. I have a Tidal 75 HOB filter that runs about 350 GPH and a powerhear that runs about 800 GPH. He does seem to struggle a little bit swimming into the current and has to swim very hard to make it through certain sections. He is eating fine tho. It is a 40 gallon Tank