Tank maid filters have a 3 stage filter network to work 24/7 they will keep your aquarium water clean and healthy.they have a bio sponge and filter carbon  ....fish farm direct review of this product. I have used tank maid filters for a few years now  I've found them to be brilliant in cleaning the tank and keeping water clean but they should not  be used really in tanks on fancy goldfish as they flow really fast and can be to turbulent on some fish i help fix this by placing filter going from back to front of tank instead of end to end .