They're Galaxias maculatus, a temperate species native to Australia and New Zealand, don't like temperatures over 25C. They are probably one of the most heat tolerant galaxias, along with Climbing Galaxias. Google says 10cm max, in my experience can get 23cm+. Need good aeration over 25C, the ones i had with my turtles died because: 1, to hot, 2, aerator for sponge filters died, leaving them filtered only by two canisters providing little aeration, 3, turtles ate them as they were sluggish and gasping for air.
Rare outside of AUS and NZ.
50g minimum. that tank is a 80g with odd dimensions.