Hi lola,

I have always had rubbermaid poly stock tanks. I did have several crack. :(
A couple of them were my fault, since I let them freeze full of water one winter. My above-ground ones I now empty and turn over for the winter. I don't have fish. I have 2 300 gallon ones that are sunk into the ground. One is a lotus bog, and the other is for plants/frogs/snakes. I do use a big deicer in the winter in that one.
It's all up to you. Sinking them half-way would keep them cooler in the summer, if that's needed, and a little warmer in winter.
I'm afraid with fish, you're always going to have raccoons trying to get your fish. You could put a run of electric wire around the ground around it. What size stock tank do you want to get? Your chances of not having coons get your fish might be greater if you don't put any plants/pots near the edge...........but then again, they're not afraid of swimming.
I've seen lots of pics on here of metal stock tanks for ponds, and people seem to like them. I liked the poly ones 'cause they're not so bright.
Good luck, and be sure to post pics once you get it going.

If galvanized metal you may want to put a liner in it - some reliable sources say the zinc in it can leach out and be harmful to fish. Of course in true internet fashion, other people say its not true, but I just have never wanted to take the chance with my fishie's lives. I suspect the oily film on new metal could be a problem too.

I have used rubbermaid also and the one that cracked was my fault and had moved 3 times and was 25 years old. I have 2 others that are just fine and at least 20 years old--they are buried with a thick layer of sand under and around them on top of our good old Georgia clay..

Me too..........the ones I have that are buried are doing just fine. Maybe my above-ground ones got twisted when I would empty them and turn them over for the winter. I think the poly ones do best when they're not moved much.

I know this is an old post but here goes. I've had a galvanized tank above ground for a couple of years ( with fish and plants)..it is becoming corroded. I think this is because of the plants etc. We have had galvanized stock tanks for livestock that lasted 10-15 years and more. The same with poly tanks too..in bad weather and freezing with no issue.

I think now I am going to bury a poly tank and skip a liner.

If you want fish, the pond must be a minimum of 2 ft deep or the racoons will get the fish. The water alone will attract racoons if there are any in the area. I have heard way too many testimonies about this..even in urban areas.