I have a SA that is about two feet. I like him a lot, but he really does not do much. If the 125 is your sole tank I would not recomend going with the lungfish. Mine is great , but I can really go a couple days without seeing him. The only reason I know he is still alive is because he is not on the floor and the food is still there. Unlike SAL mine is kind of agressive. I had a large oscar in the tank with him that he would beat on until I removed it. They were the only two fish in the tank.