Hello I ve had my pond for 20 years now and this year I got this reddish algae, it disappears at night and appears around 10 or11oclock it looks green in the evening , has a greasy feel to it, what is it and how do I get rid of it without harming the koi?
there is a PSU webinar on this subject:
This discusses id and control of algae in ponds. Other resources can be found at:
Please review the link to Planctonic algae that does turn red at times.