Does look like cyano this might be in a flow dead spot i turkey baster the sand to remove it either that or you can cut hrs of light, reduce your feed, up your cuc, or invest in chemi pure to put in your filtration hope this helps
Thats a photo of the weir ok iv dropped light hours 2 8 per day and i only feed tiny amount of flake every second day, my turbo disappeared a week ago im guna buy 4 more next week hopefully they handle the outbreak
Honestly, don't get any more turbos. There is no guarantee that they will clean up the algae, but its guaranteed that if they die, they will only contribute to the problem more.