I hope you guys know it's a back yard koi pond and not a mud pondThis question and some of the replies like Gill Blue's kinda suck. You should really stick to Texas native fish so lmb, bluegills,crappie, and whatever strikes your interest that is native in the area. A sturgeon is definitely a no go due to the summer heat. If this is a closed system pond as in there is no streams feeding the pond/no chance of the pond flooding into another water soruce you can expand your range of fish to other natives that aren't found in the area but can tolerate the heat/cold. As for this whole freezing debat as long as the pond is deeper than 4ft in areas which is what is deemed as the freeze line the fish will do fine.