aaawww. Funny fishes these Koi. My folks and my grandad kept koi for years and years and years with no special treatment at all and in the end my grandads were huge! However, mum and dad lost the best of theirs one night, mid summer, very very humid and a thunderstorm erupted. Next morning, over half of them were floating! (waste not want not, the lot went on the compost heap!!)