Does sunlight cause or increase cyano algae? I have a tank that gets maybe an hour of sun during the day and my tank has cyano bad. I didn't know if the sun will increase the amount or if it causes it. I had a nitrate spike but it's been under control for a while.
Assuming it substantially brightens the lighting, it would probably boost many photosynthetic organisms, including cyano. But I would not assume the cyano is caused by the sun (that is, will go away if you block the sun). Most people with cyano do not have direct sun, and it is very common.