oscars, my first fish. i wont buy another one though unless it's wild caught. i have had bad luck with them. they get to 9" and die. i think it's due to inbreeding or something. my water is always perfect and no other fish have given me problems.
I've never been to a PetsMart in any city without these guys. They're great in brackish and better in sand-- ours uses its tails to shoot the sand all over the tank to make it more homey, and then it wiggles down into its little divot. Great bottom feeder-- it cleans up any food other fish don't eat, and has been peaceful with bumblebee gobies, GSP, mono, and even cuddles with our brackish moray.