I am curious on your project. There must be so many factors that contribute to growth rate. Are you using different variables or just putting them outside and letting nature take it's course? It should be very interesting either way with a lot to be learned. I look forward to your results.
I understand that dealing or collecting over a certain number of a single TX non-game species requires a permit in Texas. You may need a Permit for your project, depending on how many you keep. A small number of 10 or less, would probably not require a permit.