for one hello, this is my first post on this forum. I breed fish, and to do that alot of the time I have to have very good quality water, so I used grow beds on several tanks and it works very well. I use lava rock for media and I grew kale which was just awesome. I just used a window for there light sorse and they seemed to thrive.
You might want to check out this school's aquaponics system: http://www.youtube.com/watch?v=IveNGoi5Vk4&feature=player_embedded They use only catfish in their system. Catfish have been known to sleep in puppy piles, so it shouldn't be as much of an issue. I haven't known them to be territorial.
Water temperature can be kept down naturally by setting the pool deep enough in the ground. I live in Arizona and have seen koi and goldfish survive in outdoor ponds that are less than 5 feet in the ground with ample shade and no direct sunlight - the shade being the key feature. There are water coolers available for ponds and aquariums if you can't get the temperature down. I know Lowe's carries them for ponds if you can't find a pond fish store. Catfish should be fine in Texas summers, though. My summer camp in Tyler (I grew up in Dallas) had a pond full of them and they had no problems flourishing.