I've hardly heard anyone talk about the Cairns Aquarium, it's definitely pretty underrated. The theming is amazing, with each and every animal displayed there being found in Queensland. Even though it is an aquarium, they have an entire exhibit of terrestrial species as well, lizards, snakes and insects/arachnids. They have a good amount of rare species, like the freshwater whiptail ray,
Urogymnus dalyensis (the only one on display in Australia, and one of only 2 kept anywhere), emerald tree monitor (only display of the species in Australia), Lake Eacham rainbowfish, olive sea snake and freshwater crocodile. The displays themselves are very good, with very interesting ways of displaying the animals. One of my favourites is the tidepool tank, which is a pool with 2 deep areas separated with a shallower area, which prevents the fish from moving between the deep areas. I don't know how they've done it, but the water level in the tank changes, and when the water at it's highest, which occurs every half hour or so (I think, I haven't actually timed it), the fish can cross between the deeper pools. The half-tunnel in the billabong tank is nice, and offers a good view of the freshwater whiptail ray which frequently rests on top of it. There's a nice little tunnel in the freshwater turtle tank, but it was really meant for kids and is a tad tight. However there isn't really a conservation message at all, it does briefly touch on the threats to the largetooth sawfish, but no mention of pollution/climate change, which I feel is a bit of a missed opportunity. Also the signage on the freshwater tanks is good, but for the reef section, a tank with 10 or so species will only have 3 signed!

Only sharks/rays and 2-3 large fish are signed in the oceanarium, which leaves you guessing at what everything else is!