Continual green water. UV bulb new.

[Dave 54]

All's well that ends well then Ian but you hve to ask yourself why it took so long to clear do you feed the fish two or more times per day as ,any of us do in the summer months to lay down reserves of fat for the winter , If so this may have been a factor in your problem .
Do smaller water changes as Mucky says on a regular basis , feed only what they will eat in 5 minutes and take regular readings of your water perameters and I cant see you getting a problem


Dave

 

[Ian Butterfield]

During the harsher winter months I turn off the UV and the water greens slightly and when the sun starts getting stronger it is put back on. Have always done it as the water has been fine this way. Only this year was it a problem, hence the opening question.
The fish only get fed a small amount not daily during the brighter months of the year.
Not much goes to waste either.

 

[Tula]

I'm not good with math, but googled 320 litres. ...is that about 85 gallons? Not sure, but if so.....I'd day 2 koi is a lot for that space, especially if one if 16 inches. As I said, I may have my numbers incorrect.

At any rate, glad things are clearing up for you. I myself and going to try some quilt filling for fine particulates....just have to figure out how I'm going to do it