Goldfish In Huge Outdoor Tank

50F for fancy/fantail/roundbodied goldfish. it sounds like he (and the goldfish) have lucked out. there is nothing about that setup that i would suggest. if you want goldfish, dont cut any corners, most likely they will come back to haunt you.

When I lived in Northern Colorado, I had one of those pre-formed plastic ponds that was about the size of a bath-tub. A friend of mine put several feeder-type comet goldfish in there so that we could watch the neighborhood raccoons try to catch them. Each winter the tiny pond would freeze solid. Each spring, the fish were swimming around happily.

I do suspect that there must have been some layer at the bottom that did not completely freeze, but the pond was only 2 feet deep at the deepest level.

However, I suspect that you can't just toss goldfish into freezing water, they probably have to acclimate to the conditions over a long time.

Since they are outside they are probably getting plenty of insects to eat durring the summer. I feed my pond fish a few times a week and sometimes they dont even eat it. They will thrive in cow tanks. Not sure why. When I was in high school we had a neighbor that moved and gave me and my brother a 20 gal with 5 or 6 fancy goldfish. I cant remember why, but for some reason we put them in the cow tank outside. It wasnt long until we had forgot all about them. bad I know
Anyway I went out one day in January freezing weather to break some ice and top off for the horse and WOW there they were frozen. I thought... uh oh. I forgot they were out there. Didn't have anywhere to put them, they were frozen in ice, and I figured they were gonners by then anyway. A couple of them were barely moving down in the bottom. That spring they were just as big and active and bright colored as when we put them in. In fact, they will grow like crazy outside. It must be insects thats all I could think of. I have a small garden pond now, and I dont do anything to my goldfish in the winter, dont even filter the water. I top it off as it evaporates and on warmer days I feed them. There are no bugs here in the winter, too cold. Every critter, dog and cat in the area drinks from the community bowl LOL.
I would think in TX they would do great as the water shouldn't even freeze.

I should have suggested putting the tank in an area that is shaded or sheltered. Especially if you are using the black poly kind of tank. Durring the summer the sun can really heat up the water. I am assuming you are just setting it on the ground, not burrying it under the dirt? you might try putting some cut cement stones around it in layers and fill in with dirt between the tank and the stones to help keep the temp cooler and steady. If it is really hot you can add a fountain to circulate the water, keep it agitated for oxygen. That probably wont be needed unless it is kind of crowded.

i have a 150g pond with goldfish and koi in it (building a MUCH bigger one this summer) and its never even barely froze, even last november when it got like 10 degrees. we just used a trough heater and it stayed about 40 degrees. haven't lost a single fish to cold yet. i am considering using a large livestock trough as a temporary pond for the fish until we can get their real one built out at my parent's new property, but it will have a pump and filter and plants and everything, not just a stagnant puddle.