If you have to use an oxidizer such as PP or O3 to keep your pond at a decent ORP level....say at least 250mV.....the load (fish,their food and other organic polution) is too much for the engine (aeration and filtration).
With 2 nexus on 10,000gallons with 35 koi.....ORP this morning was 370mV. If I can keep the ORP over 300....ANYONE can!!!
