Are you restricted to tanks, or can you get access to a pond, livestock tanks, or other larger containers?
I think a good project would be to compare growth rates between two similar food species kept under similar conditions; for example, two species of tilapia, or two catfish. I would be very interested to see the differences in growth rates between the standard farmed freshwater "prawn" Macrobrachium rosenbergii and one or more of your Texas native macros, like M. carcinus or M. acanthurus.