Small fish in garden

[ThisNeatPinkHare]

Hi, we are thinking of getting fish for the garden. I heard you can keep gold fish in a water butt. We have a normal sized (210 litres) as well as a smaller. Would this actually work? It seems to me a water butt is deep but not wide - would fish have enough space? Our water butt is next to a fence, so it shouldn't overheat. I am happy to add plants, filtration and aeration as needed if this makes fish a possibility - but I though gold fish become very big??? I could have gold fish in a water butt if I'd have to rehome them after a few month... Are there any better alternatives or does it really only work with a proper pond? What about rice fish? Could we have them as long as we secure a metal crate or similar over the water butt?

Only just seen your post.
I wouldn't keep fish in the way you're thinking if it's the usual shape water butt. Too dark/deep inside, a difficult environment for goldfish who like to feed from the surface, bask in the sun occasionally and speed around at times; ergo, need more width less depth. Also you'd want to be able to see them easily, would you not?
Please look at Oz Ponds on YouTube. He has dozens of videos, all about his ponds and the way he builds natural filtration into them, and yes, he's even got one on his BARREL pond which could give you inspiration. I have copied one of his designs, albeit on a much smaller scale, very successfully and haven't had to clean a filter for around 4 years.