I have a 800 gallon fish pond that have about 10 gold fish and to small koi in it i have a 11 watt uv light ?

Question

and one bio box is it possible to have two clean of water to make 5 gold fish die . i had the water checked and it's all good . a pond place told me the water could be to clean that all the good stuff is taken out of the water for the fish. could this be true

Answer 1

One koi needs 1000 gallons. The "good stuff" is the beneficial bacteria. That lives in the substrate and filter. Unless you put an antibiotic in the water, there is no way it could be "taken out".  If anything it was predators or a parasite in your fish.  

Answer 2

what do you mean by too clean water? did you do some water changes?  it could be the chlorine.  

I don't think good water condition could harm your fish.  Even without the good bacteria it will not kill your fish.

maybe your UV light got a ground on its wiring inside most pond on their UV light 24 hours a day and nothing happen.

you can join the yahoo group and ask the pros there what can they say about the UV light

kOi keeper & goldfish keeper

http://pets.groups.yahoo.com/group/world...

http://www.geocities.com/koiphilippines/...

http://www.youtube.com/watch?v=ArAlwupRy...

Answer 3

Yes, if you cleaned it too much and removed too much of the good bacteria, it can kill your fish.