Well we ended up taking the pump into the store and it was working fine for them. Got it back home and put it back in the tank and it was making the same noise. Went back to the store and told them about it, they said it must be vibrating against the tank so we should just bring it back and they'd give us a new tank (the filter/pump for these tanks is glued onto the back of the tank) so Friday we got our new tank.
No problems so far and it's been running for 3 days now. I keep wondering if it is even working since it is SO quiet but all is good with it!
Thanks for the help!