Back when I had T5's, while programming a sunrise/sunset lighting, I had an outbreak of cyano. Spoke to the LFS and was advised 2 things:
1: Lights has been on for more than 8 hours, fixed with a timer.
2: I was recommended to get Two Little Fishes GFO media.
Since then I have not had any issues with either Cyano or any other bacterial or algae related problem.
You also have to give it time if you've added a cyano remover chemical and do water changes to completely eliminate it.
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