I have seen some fish tanks made of fencing bent into a circle, and then a liner put inside. Do these work well? It seems like a quick, easy, cheap way to make a huge tank. There must be a reason that I do not see these very often.
The main things against it would be trying to fold a liner into a round tank is challenging and plumbing through such a tank while quite possible is a bit tricky.
Here is the part of my BYAP big system thread where I built my cattle panel fish tank