Why does cyano grow here…and only here?

[Huskereef]

Im at a similar spot. 2 year old tank, kicking goals with nice sps and good growth then bam - cyano. Mine tends to die down over night but by the end of the photo period it’s a crime scene.

I’ve tried no and low lights during the day and both strangely have little effect except to effect the SPS.

It’s very frustrating.

Same exact problem I’m having. Mine isn’t affecting my sps one bit, thankfully. Polyps are still fully extended and everything is still growing. But at the end of the photo period cyano has spread immensely vs beginning of photo period.