I would like to find a small filter with a medium to high flow rate for a 4g female betta tank. i like to use readily available carbon inserts. i know some people dont use carbon anymore but i like it. i dont like the whisper filters they are too big and the flow is not good enough. i like the filter that came with my petco bookshelf tank but its only sold as a kit. any help please??? i was thinking of the small fluval internal filter with spray bar i havent tried these yet. what do you use?