i gave my 2 goldfish, Patches & Sushi, away to my neighbor and good friend because i am moving to the mainland and something really horrible happened! normally, i will stack a couple of rocks just under the filter where the suction part is, just so the fish cannot swim under there and risk getting their fins sucked into it (they're fantails). But when Stacy changed their tank this last time, she forgot to stack the rocks and Sushi's rear fin got stuck in the filter where the suction is the strongest and part of it was torn off!! i was mortified. she assured me that her fin would grow back, but i just didn't beleive that. is it true that fins will regenerate if something happens to them?