Sick Koi's

[bsr8129]

We have a premade pond that is roughly 250 gal or so, we have had it for 3+ years and just recently have been having issues, we have lost 2 fish in the last 3 months, and currently we have 2 fish that are swimming on their sides, what does that mean?

We have taken the fish out and are cleaning the pond this will be the second time in 2 months, we have a filter with UVB. currently there are 4 koi from about 3in to 6 in.

any help on what is going on would be helpfull

 

[bunnymp]

Have you tested the water? Ammonia, nitrites. anything?
Do you use benefical bacteria?
What type of filtration do you have?
Where are you located? Have you started feeding yet?
What is the water temp?

 

[DrCase]

ALL VERY GOOD QUESTIONS bunnymp

 

[DrDave]

Has anyone sprayed malathion near the pond recently?