Hi, I will have another go some time. If you have a look at the fish second from the bottom left hand corner you might just catch the two greenish iridescent spots above the eye which, IMO, separate this species from anything else in the ACT.
I can't see the history but Im guessing the proposed ID was Gambusia holbrooki? Agree its not enough for a positive ID, but is most likely species in that location. Oriental weatherloach are known from the location but its clearly not that species.
In what time frame they would re-appear if removed is unknown.