If I had a pond I'd put him in it, but the best I can do is a bucket, considering as I have no room for a pond. After talking to my dad, I don't think my fairground goldfish is a comet & he should only double in size (become about 15cm long) so that helps a lot. My plec is 20cm long & fully grown, so are my fancies. Knowing that I don't have a comet, would I get away with a 200-250 litre tank considering as the fairground goldfish won't get as big as I expected?