The tank looks nice and the controls for the camera are fine. What you could improve are the controls for placing plants and stones: Instead of the x,y,z arrows it would be nice if I could move plant with the mouse along the ground surface (adjust the height automatically). For the other props (wood & stone) it could be nice if they could just be dropped and are then placed via a physics simulation using colliders.
I had a bug once where one of the fish was trapped outside of the tank.