In India, West Bengal is the leading state in hatchery-based seed production (spawn, fry, advanced fry) of major carps and other economically important freshwater ﬁshes. Dissolved oxygen is the most critical parameter of water quality and basic necessity in ﬁsh hatcheries, nursery and grow-out ponds. Hatchery ﬁsh seed production can be limited by the dissolved oxygen content of circulating water. Progressive ﬁsh breeders in villages of West Bengal have overcome and eliminated this problem by designing simple but eﬀective means of water aeration to improve dissolved oxygen in hatchery water supplies, maximising survival of fertilised eggs, hatchlings and spawn. This article describes some of the techniques that have been adopted using low-cost and recycled materials.