Working in a pet store is so much fun. I worked at Petsupermarket for about 6 months, then it closed. (They're opening a new location). I was a general clerk, but I was in the fish department the most, because I was the only one with a lot of knowledge about fish. It really is a lot of fun taking care of all of them, but it is tough work. Try doing a water change on a whole system... It literally takes hours, but is well worth the effort. Working at a petstore is also VERY helpful with the costs... I had a 50% off on fish and 25% on merchandise. Very, very helpful.
Enjoy it! I know I did!
PS: I hope your manager will be like mine was. (Very fishy person). I got to see the fish orders and help order some fish. Also, you get to order pretty much what you want! And those huge fish lists... ahh amazing. It makes you want to get all of them.