so within the past 3 days, my percula clown and one of my damsels decided it would be fun to swim up into the powerhead and get stuck. i found them and freed them, but it was too late, and they were dead by the time i got to them. so, are they just dumb or is there something im doing wrong? for more info, they are in a 30 gallon with live rock and 2 other damsels, along with about 4 hermits.