I would talk with the people on shark ray central... they really know their stuff when it comes to this.

I assume black banded bamboo you are referring to the brown banded bamboo? If so, once an adult it will need a footprint of 45-50sqft. If you wanted a mating pair the footprint will be even bigger.

Since in south Texas you will need a good heater setup for the winter but more importantly a massive chiller.

I have seen some nice DIY shark/ray ponds and they are usually inside or blocked off from the elements. Plus they have enough filter equipment to fill most peoples living room.

On the shark/ray forum they had a really good indoor setup using wood, sealer and pond liner.

As for evaporation... you will need a automated RO/DI top off especially during the summer. With my current setup inside the house I lose ~3.5g of water a day with the tank temp at 78 and house temp at 72.

I do not know how other elements that could blow into the pond would react with the sharks.

Good luck!