Alright, my friend has a small and will now be extending it a little bit. I was thinking that he can make part of it as a semi-jacuzzi thing that blends into the pond (with fish). The swimmers/human part of the pond will not be accessible by the fish (screen). Also, it will be cleaner. I was thinking a nice filter or somehting of the like. My real question is... ...would it be possible to make the water clean enough for humans, but also liveable for the fish?