Adjustable flow control knob  Excellent for small aquariums under 10 gallons Great betta tank filter This nano hang-on-back filter is excellent for aquariums under 10 gallons. It moves 52 gallons per hour and has an adjustable flow knob for fish who need lower flow such as bettas. It comes fully equipped with media and an intake sponge. However, upgrading to our mini pre filter sponge is ideal as it offers greater coverage of the intake tube with less clogging from debris. Hot rod this filter by adding coarse sponge to the media portion rather than the provided cartridges. Dimensions: 4 inches x 5 inches x 5 inches Wattage: 3 Watts 52 gallons per hour Note: May not fit on some rimmed aquariums and is best for rimless tanks and 5 gallon and less rimmed tanks