I am enclined to think it is closer to being an Endler than a guppy because of its size, it is still tiny even my young male guppies that are now way near as mature as this guy is dwarf it, and it is getting more and more fluro sort of colouring in light it just glows and sparkles. It quite possibly does have guppy in it but I have not seen the usual feral guppies that we have in Australia in this creek. Usually feral guppies in Australia have grass or snakeskin pattern and females are totally devoid of colour with maybe a small splash of black speckles in the tail.
If it stops raining this week I will go back to the creek and see if I can catch any more of these. The creek does have gambusia as well as at least two types of native rainbow fish, at least two types of gudgeon, macrobachium shrimp and glass shrimp (Paratya australiensis), spankled perch and possibly even Barramundi in the deeper sections.