Blazer, I've got a piece of advice for you;
It's easier to beg forgiveness than to ask permission.
Just set it up anyway, and then when your parents don't like it, you can just say, "Well, it's set up already. I'm really sorry, I didn't know you'd be so mad. But look how cute these fish are?"
Just in case you wanted to try it (I was going to put an emoticon here, but I hate emoticons, and all these ones suck).