Is it bad to...

[vanwassup]

buy a fish that you know is going to outgrow your tank if the petstore says they will take it back in a few years when it is bigger? I am expecting my RedSea Max in a few days and I found a cool aquarium/reef store. They had lots of hippo tangs that were quite tiny. My daughter is four years old and she really wants one in the tank. I'd like to humor her, but I know hippo tangs get very large... so I guess my question has two parts

1. Is it unethical to knowingly get a fish that will outgrow your tank - with the intentions of returning it to the store (they'd give me a credit towards another small one when the baby grew up a little bit)?

2. How long would it take a one inch hippo to outgrow a 37 gallon tank?

Thanks,
Vanessa