Santa Monica Filtration HOG.5 Hang-On-Glass Upflow Algae Scrubber ATS Aquarium Filter Turf Saltwater Replaces Chaeto Reactor Protein Skimmer Sponge Canister Pellets Zeo Waterchange Probiotics Removes ammonia, nitrite, nitrate, phosphate, nuisance algae, CO2 from your aquarium water Can't overflow onto your floor, because it is always under water You can feed some of the algae to your fish or snails! No electrical parts go in the water; only air Can go on aquarium or sump wall if 1/4" (6mm) thick or less.