I have just bought a Plasterer's Bath. This is a 4ft x 2ft x 1ft builders quality plastic tub, virtually indestructible, and will be used as a test tank. It was getting a bit difficult to take larger models up to the bath (and clear up afterwards). This can sit outside my workshop and be filled with rainwater fro the Butt.
It also makes a great play pool for Henry, the Labrador, in the summer.
Price, delivered, is about £40. Do a Google search for Plasterers Bath, there's quite a few available.
John