SUNSUN HBL Fish Tank Biochemical Filters 3 In 1 Filter Hang on Back (HOB) Waterfall Filter for External Fish Tank Oxygen Pump. These are great compact filters that offer biological, mechanical and chemical filtration. Here are the specs and features:

Model:HBL-701
Voltage:220V/50Hz
Power:8W
Filter Circulation/Output: 600L/h / 160 gal/hour
Aquarium Capacity/Tank Size: up to 40 gallons 
Power line length:1.5m
Built-in filter material:2pcs Filter cotton,2pcs Filter plate
Retail on Ali Express: $43.95 + 7.84 Shipping = $51.79 + Taxes
Price: $25.00
 
Feature:
Energy saving.
High efficiency filtration waterfall design flow, it has a good filtering.
Ultra-quiet, motor running will not bring noise, excellent mute, will not affect the life and mood.
Optimal flow is realized by adjustable flow regulating valve.
Restart motor by filling the filter with water to avoid motor burn out.
Suitable for fresh water and saltwater aquariums.
 
Package included:
1 x Hanging Filter

Note:
1.Please fill up with water before starting. It will help the filter quickly into normal working condition.
2.Please make sure your aquarium tank's wall can hang up this pump.