Reds have to be 15" because the smaller ones cannot tolerate the low salinities. However I think the point is mute as even larger fish wouldn't survive in a smaller pond. It would just get too cold. The bigger lakes that are cooling reservoirs stay hotter because of that and also stay a more steady temp, something a smaller pond won't do.
The bull shark is the species that can tolerate freshwater the best. They have been found as far north as Illinois in the Mississippi.
Peacock bass would not survive in your part of Texas either. If you can't overwinter Mozambique Tilapia, you can't overwinter Peacocks.
That is the problem with the "exotic" pond fish... Where do you get them from? Unless you have a wild source, you are SOL. I'd love to get my hands on some freshwater drum, but they are not found in the wild around here.
Esox species may do well in the southern lake or reservoir, but I am not so sure about them doing well in a smaller pond. Perhaps chain pickerel as they have a far south native range, but tigers or NP, I would be doubtful about.
In smaller ponds, HSB do fine until they hit 4 or so pounds. George can share his experiences. Once they get over that size, they require cooler higher DO waters and die. An old member Meadowlark has lots of HSB experience in Texas waters and experienced numerous die offs in the summer when the fish got larger.
