you dont even need a filter. I didn't use a filter on my 75 gallon. If the plants are growing, they are filtering the water. If you do 2 waterchanges a week you shuld be fine. IMO, no nano tanks should have filters. They are too big for such a small tank,and make it look ugly.
75 gallon, fillstar xp2 with inline reactor, 12 Lb pressurised co2, 4.2 WPG-corallife 3x96 watt PC-, fluorite/silica-sand substright.