Abstract: Tropical fish eggs are placed on a slate and fertilized and the slate is placed in an incubator in a water circulator which includes an air stone for drawing water across the eggs in the chamber containing the slate while air bubbles rise to the top in the adjacent chamber thereby maintaining a smooth, gentle water flow simulating water movement generated by the parent fish. When small fry begin to appear they are placed on a mesh screen above the bottom of the incubator and water inlet pipes on the bottom of the incubator draw water downwardly past the eggs and small fry and that water is then moved upwardly under air pressure injected into a vertical main pipe and fed back into the top of the incubator tank.