grdesign@talk21.com asked: Water parameters are fine. I have 8 koi from 30cm to 45cm. Pond is 6feet deep. Pump fed. Gravity return. 4 bay filter (1 mechanical, 1 K1 media, 2 Jap matting) Hi blow 80 airating fillter. Water is very clean i.e. no suspended solids. Fish are showing no sign of ill health.
Not algae [...]