210m deep, 9.5m in length and 850m width? Since it is a fibreglass kidney shape I think you have the measurements incorrect. I do not know of any fibreglass fish ponds deep enough to go diving in. I suspect you are missing some m's in there.
The largest preformed kidney shaped pond I could find after a quick search was 1200 x 900 x 420mm deep, capacity 220 litres.
I agree with Ira though, it needs filtration, especially if it is actually the size I think it is and not what you have stated. I fear the water quality deteriorates rapidly with 15 fish in it.