These fish looked different to the gambusi. THey were four times the size of the large females. They came up from the depths, swam along the surface and then disappeared back under. Its quite colourful. But I don't know what they are. The dorsal fin/s? has a reddish edging.
Wondering if this is Hypseleotris galii - Firetail Gudgeon - https://tooheyforesteec.eq.edu.au/support-and-resources/teacher-resources/firetail-gudgeon ??