I think stores sell those sharks because they know people think they're cool, will buy them, and most likely end up either killing them or getting rid of them when they get too big. Either way, the fish store doesn't take them back, so they get to reap the benefits of selling them without worrying about actually taking care of them. What do they care? They have the money...

I love corporate responsibility.

I think my next tank will have sand substrate... thanks for the tips, Dizz, I probably will just rinse a little at a time. More thorough that way. Plus, I can do that indoors in the air conditioning. It's too hot here.