Warm, oxygenated water from main aquarium circulates continuously through the breeding box with the use of an air pump (sold separately), so that fish enjoy the same conditions as the aquarium. Additional heaters or filters not required. ? Multi-Purpose ? Safe & secure tank for breeding, isolating or acclimatizing fish Space-saving design, easily installs on the exterior of the aquarium ? Fish fry slip through the V-shaped separator and are safely segregated from adults