umm he all ready has koi in the pond... My friend live in MI like me.PhilBen;4523599; said:If the pond is 10ft deep and the size you say. There is no reason why you could not put Koi in. That of course depends on where you live. But it is deep enough to cater for most places as they would get the heat from the bottom in the winter. Where did you say you live ?