Koi keeping for beginners Live help on the message board Koi medicines, chemicals and supplies are available . Simple submerge a water pump and aim it at the water's surface. The water will break the surface without causing undesirable visual disruption. To prevent the pump from clogging, you can use a pump sock .
Fish appear fine, for now anyway.
Very, very important phrase here, and you hit it squarely on the head. Excess ozone, even a tiny little bit, will tear the hell out of your fish in very short order. You are absolutely correct. There is no difference whatever between an ozone molecule created by UV as opposed to one created by a corona-discharge device. You can get some really insane outputs from a small corona discharge.