Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Sierra: Mosquito netting over the tank is better than expecting fish to live in the full sun in Texas. The water will get WAY too hot for almost any kind of fish.
Anywhere that anyone wants to keep fish outdoors:
Larger volumes of water will maintain a more stable temperature than smaller volumes. 100 gallons may work in a situation where anything smaller over heats. Aerate the water for best oxygen levels. A pump set up to create a flume does this very well, and water falls or short streams that expose the water to more air are very good, too. This can also allow for evaporation that can cool the tank.
Monitor the temperature and provide shade to keep it cooler in the summer. Perhaps under the shade of a tree, or arrange an umbrella or a shade cloth for the hottest part of the day.
If it freezes in the winter the glass or plastic tank may break. Do not leave it out. Obviously, this also means housing the fish indoors in the cool season.
There are laws about catching and keeping native fish. Be familiar with them. Each state varies, and each country varies.
Even so, native fish live in much larger bodies of water, and can swim down to cooler water if the surface of the lake warms too much, and a warmer pocket in the winter. An aquarium does not provide that sort of protection. So, just because a fish is adapted to your climate does not mean it will live in a more extreme variation of that climate.
A pond, which is sunken in the ground, is better insulated for protection from temperature changes.