Tetra makes a good filter that hang on the inside of the tank. Here it is... http://www.petsmart.com/product/inde...028&lmdn=Brand
I have one of these that has lasted 10 years. Something I just did with mine is remove the carbon that comes in the cartredge (VERY EASY), and put some biomedia in it. Works great, and you can adjust the noise level on it. (Higher water = less noise. You can even make it completely silent, which is handy if tank is in bedroom). I have 2 of these. I used to run both of them on my 10g betta tank until I took the tank down (today). Definetly great filterts. SUPPER EASY to use. Just plug it in and it works.