I've ordered from the marine center before, I think that they offer some great fish that are on the whole, very healthy. I'm not sure why they would list the minimum tank sizes the way that they do. Maybe they mean the minimum tank size at the time of purchase? (when the fish is 3-4")????? I don't know, but overall, i must say that the marine center is a great mail order place (especially if you're looking for rare stuff that your LFS wouldn't carry).