AC allows fish on board in their cabin, however airport security does not like it and will hassle you about the water the fish is in as being a security risk. I have successfully brought both fish (guppies) and hatchling turtles on a domestic AC flight with their knowledge. I would not do it again. Officially, turtles and all reptiles are not allowed. They only allow domesticated small pets (i.e. cats, dogs and rabbits) in the cabin.
You need to ship your reptile as checked baggage. The cargo-hold is insufficiently heated, and even though they say it is heated, the heated cargo-hold ranges between 10-16C. Make sure you use a Styrofoam box within a cardboard box and heatpack, even if it is warm outside, it gets very cold up there. There are is an extra fee for checking your animal in cargo or bringing it aboard. Check the AC website. But generally, staff at the different levels know jack-squat.