The reason I asked the size is that I have 3 large 1/2 wine barrels at my front door where I have been keeping goldfish for the past 3 years. Whenever the pH gets out of whack or the nitrogen levels get a little out of the control of my water plants in the summer, I bail them down by about a 1/3 and add fresh water. I also rinse off the roots of the floating plants too with fresh water at the time.

I probably wouldn't have to do that, if I was a bit more careful regarding the quantity of food I give the goldfish, but a couple of the fish have become my buddies and they beg whenever I pass by. Never give goldfish names, they start developing personalities with which you can become quite attached. Initially I just plunked a few 35 cent feeder fish in the tubs for mosquito control, but now they have become more the point of interest for me than the damned plants.