i have a 150 sitting in my garage but i have been thinking about a stock tank. my stock right now is a mala wolf, a ck, and a pike cichlid. may get rid of 1 or 2 of them but i have been thinking about getting rid of all and getting another lungfish
same and for the same reason, the tank so u can look in to it.
if you were gonna go with some kind of rubermaid type look down format check out some of derekp's post, he has a 700 gallon metal water tank type thing from a tractor supply place that was relatively cheap, and really would open up your options and probably be more reliable down the road.