PENN PLAX World Aquarium Filter, Small Helps keep your small aquarium healthy and looking beautiful Specifically designed for small aquariums up to 5 gallons Fits almost any small aquarium shape or size and is compatible with any air pump Helps keep your small aquarium healthy and looking beautiful Specifically designed for small aquariums up to 5 gallons Fits almost any small aquarium shape or size and is compatible with any air pump Helps keep your small aquarium healthy and looking beautiful Specifically designed for small aquariums up to 5 gallons