Hydra Filtron’s 4-Stage Water Purification, goes beyond the conventional 3 stage filtration (Mechanical, Biological, Chemical), with the incorporation of the revolutionary Hydro-Pure technology that uses Hydroxyl Radicals (•OH) to accelerate the startup time from the usual 4-5 weeks to within 1 week, reduces water odour, and retains a crystal clear tank. The Filtron 1500 is designed for 150-600L aquariums.