At Petco they sell something they called a Betta Bowl Cleaner or something along those lines, but it was basically a turkey baster with a blue top. You can try that, it's pretty time consuming though.
Also I just ordered off amazon a mini gravel vacuum that's supposed to be for small tanks, I can post a link to it when I get on a computer.. =) hope that helps
Here's the link for the little vacuum I ordered, I haven't gotten it yet so I don't know how well it works personally though:
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1
=)