My filter came with the 5 g Hawkeye tank and even with the plastic baffle, it still swirled the water around too much. So I took a piece of sea sponge that I had used for craft painting and I tied it to the output with fishing line. I think any sponge will work but the sponge has many holes and doesn't block the 3 little ports. If you have a differnt filter like a waterfall, just anchor a sponge on there to restrict the flow. It also will start collecting those good bacteria, win/win with happy fish.