Flat-headed Gudgeon Philypnodon grandiceps were bred in ponds and aquaria at the Narrandera Fisheries Centre at temperatures from 18.0 to 28.0°C. Breeding in inland rivers probably occurs between October and April. An abundant food supply was essential for initiating spawning and the breeding display was recorded.
Eggs were demersal, transparent, telolecithal and an elongated tear-drop shape with an adhesive disc at the pointed end. They measured 1.2 - 2.2 mm in length by 0.7 - 0.9 mm in width, and were attached in clusters to solid objects. Oil globules were small and numerous at first, but coalesced to a single oil globule halfway to hatching. Eggs hatched in 4d 20h to 8d 8h after fertilisation at temperatures of 15.9 to 22.6°C. The total length of larvae at hatching was 3.15 to 4.32 mm and eyes were fully pigmented. The prolarval stage terminated at about 3d 12h after hatching, when length was 3.93 to 4.69 mm. The characteristic dark spot at the base of the caudal fin was present from the mid prolarval stage onwards. Males and females matured at one year old and were short lived. The largest fish collected was 11.0 cm TL. Up to 2020 ova were present in the ovaries and the Gono-somatic Index (G.S.I.) reached a maximum of 11.92 in females.