do you have a picture of it?
If you cut the top of some types of tanks you loose much of their structural integrity and would then need to add additional support to them.
Yea, I would caution that if you cut the top off of that, you will need to do some extra bracing or supporting of it. Now perhaps if you leave the ribs in place and just cut a hole between the ribs in might work but it won't give easy access to the whole tank at once and wielding a big net would be difficult.
I'd stand it up on one end and cut the top off - maybe bury it or part of it in the ground.
That is a long tank, think about trying to net fish from it before you go forward.
I would guess it would be pretty easy to build some bracing along the long sides. If the distance isn't too far to travel, I might go get this. He wants $500 for it. Thanks for the help!
I'd sleep on that one for a while. That's a lot of money for a used tank that you intend to cut up.
TCL made a large tank using a liner. Perhaps she can link you to some info.
I like my round tank and it was expensive. I don't regret buying it.
If you stand the used tank on end and cut the other end off, you'll have a round tank. You probably would not want to make it more than 5 feet deep, I would think. I wouldn't take the plunge on that one just yet, not at that price. Keep thinking.
Do some searching for plastics companies, especially roto molding companies. Most of them probably make a few different aquaculture tanks. If you can find one that is not too far from you, contact them and see if there are any factory seconds you might get at a discount. Most of the factory seconds that they sell will just have something cosmetically wrong with them like scratches or the color wasn't quite right, the ones that are not structurally sound they usually re-grind.
Oh and the white liner is durascrim which is great for rectangular troughs but I don't think you are going to manage to make a round tank with it. The liner and fence panel tank I made used EPDM pond liner and has lots of folds or pleats to make it into a round tank.
18,000 gallon tank, anyone? Maybe the small one, 2,000 gallons?