Eggs are fertilized in the pouch. The developing embryos are aerated, osmoregulated, and nourished in the pouch. The hormone prolactin initiates enzymatic production of a marsupial fluid which nourishes the young in the pouch. At hatching, the young are well developed and independent and receive no further parental care. Males remate within hours of giving birth.
Seahorses are monogamously pair-bonded.
In Hippocampus fuscus and H. whitei, one male and one female mate repeatedly and exclusively. If a male has given birth, check the tank thoroughly for young. They will normally be born in the early morning and almost certainly before noon. If a male bends and thrusts as if giving birth, but no young are released, he is almost certainly going through courtship behaviors, even if no female is present. It is easier to rear larger young, which is not necessarily a species with larger adult size.