Sorry. They're illegal. Here is the list according to Texas F&W:
TEXAS:
In order to manage and conserve our natural resources, Texas Parks and Wildlife Department must protect our state waters against the introduction of non-native aquatic species. Fish, shellfish, and aquatic plants that are not native to Texas may compete with native animals and plants for food and space.
The organisms listed on this page are legally classified as exotic, harmful, or potentially harmful. No person may import, possess, sell, or place them into water of this state except as authorized by rule or permit issued by the department. For more information, contact Joedy Gray, (512) 389-8037.
Fish | Shellfish | Aquatic Plants
Fish
Lampreys, Family Petromyzontidae
All species except Chestnut Lamprey, Ichthyomyzon castaneus and Southern Brook Lamprey, I. gagei
Freshwater Stingrays, Family Potamotrygonidae - All species
Arapaima, Family Osteoglossidae - Arapaima gigas
Dourados, Family Characidae, Subfamily Bryconinae -All species of genus Salminus
Rhaphiodontid Characoids, Family Characidae, Subfamily Rhaphiodontinae
All species of genera Hydrolycus and Rhaphiodon (synonymous with Cynodon)
South American Pike Characoids, Families Characidae and Ctenolucidae
All species of genera Acestrorhynchus, Ctenolucius (Boulengerella) and Luciocharax (Hydrocinus)
African Pike Characoids, Families Hepsetidae and Ichthyboridae - All species
South American Tiger Fishes, Family Erythrinidae - All species
African Tiger Fishes, Family Alestidae, Subfamily Hydrocyninae - All species
Piranhas and Pirambebas, Family Serrasalmidae, Subfamily Serrasalminae - All species
Freshwater Eels, Family Anguilliidae - All species except American Eel, Anguilla rostrata
Swamp Eels, Rice Eels or One-Gilled Eel, Family Synbranchidae - All species
Electric Eel, Family Electrophoridae - Electrophorus electricus
Carps, Family Cyprinidae - All species and hybrids of species of genera Ctenopharyngodon (Grass Carp), Mylopharyngodon (Black Carp), Aristichthys (Bighead Carp), Hypophthalmichthys (Silver Carp), Cirrhina (Mud Carp and relatives) and Thynnichthys (Sandhkol and other Thynnichthyid Carp)
Rudd and Roach, Family Cyprinidae - All species of genera Scardinius and Rutilus
Old World Breams, Family Cyprinidae - All species of genera Abramis, Blicca, Megalobrama and Parabramis
Old World Chubs, Ide, and Dace, Family Cyprinidae - All species of the genus Leuciscus
Asps and Yellowcheek, Family Cyprinidae - All species of the genera Aspius, Pseudaspius, Aspiolucius and Elopichthys
Giant Barbs, Mahseers, and Catla, Family Cyprinidae - All species of the genera Tor and Catla and the species Barbus tor (synonymous with Barbus hexagoniolepis)
Walking Catfishes, Family Clariidae - All species
Electric Catfishes, Family Malapteruridae - All species
South American Parasitic Catfishes, Family Trichomycteridae, Subfamilies Stegophilinae and Vandelliinae - All species
Whale Catfishes, Family Cetopsidae - All species
Airsac Catfishes, Family Heteropneustidae - All species of genus Heteropneustes
Pike Killifish, Family Poeciliidae - Belonesox belizanus
Marine Stonefishes, Family Synanceiidae - All species
Tilapia, Family Cichlidae - All species of genus Tilapia (including Sarotherodon and Oreochromis)
Snakeheads, Family Channidae - All species
Asian Pikeheads, Family Luciocephalidae - All species
Old World Pike-Perches, Family Percidae - All species of the genus Stizostedion except Walleye, Stizostedion vitreum and Sauger, S. canadense
Ruff, Family Percidae - All species of genus Gymnocephalus
Nile Perch, Family Centropomidae - All species of genera Lates and Luciolates
Seatrouts and Corvinas, Family Sciaenidae - All species of genus Cynoscion except Spotted Seatrout, Cynoscion nebulosus; Silver Seatrout, C. nothus and Sand Seatrout, C. arenarius