Use a sponge filter - it will keep the tank cycled, and you can do a water change once a week (after the tank is cycled). The Duetto Mini is too small. It hardly has any media room. I tried to use it in a 3 gallon tank once and it didn't provide enough filtration. The Whisper 10i is too strong IMO
, and you have to use the media it comes with, which isn't very good for keeping the tank cycled. The sponge filter is perfect for a 5 gallon tank - it won't make a lot of current, especially if you use it with a gang valve.