When I do a WC & gravel vac in my 29 gallon tank, all the fish go to the opposite end from where I'm vacuuming as if they are terrified of it. The fish in my 75 gallon are totally opposite. The angels and tetras swim right up to the vacuum tube and even try to grab the particles as the go up the tube like their after food. No stress in this tank during WCs. They think is play time. Anyone else have fish that enjoy water changes?