The Tom Continuous Hatch 'N Feeder Brine Shrimp Corral can be used in both marine and freshwater tanks. The eggs will start to hatching in 18-24 hours. Hatched shrimp will swim out into the aquarium water as they mature. DOES NOT INCLUDE the necessary air pump or brine shrimp eggs. We recommend the TOM Stellar S-20 Silent Air Bubbles Aquarium Air Pump and the SF Bay Brand Brine Shrimp Eggs.