Fish on board? (not fillets)

[philaw]

This is just for fun, really, but has anyone ever kept pet fish on their boat? I was thinking that keeping freshwater fish would be too much on the sort of small catamaran (limited space inside) that I'm getting, but it ocurred to me that a hardy seafish might do okay in a small tank with a little filtration. You could change some of it's water five times a day very easily by lowering a bucket over the side!