You should look at this one at Drsfostersmiths :
Aquarium Filters: Whisper In-Tank Filters
It's by Tetra Whisper In-Tank Filter It's a Bio filter and is for 2-10 tanks It's on sale for $12.69
I have a coupon code that you can use for tomorrow that gives you 50% off of ground shipping the code is 3384/2145 good for May 2009.
This filter is so much better then that one you picked up at Petco. Compare this to the one that you posted from Petco and it even looks much nicer. For a little bit more money you get a better filter and don't you think your fish are worth it.