Sounds like cyano
. Cyanobacteria is an indication of a nutrient problem in the water column. I would cut back on feeding minimally and 3 days a week. Siphon out the cyano
that you can with some airline tubing and do water changes and water top offs with ro
water since nitrates and phosphates can come in through tap water. Blacking out the tank for several days will assist as well, but will return until the nutrients it is feeding off of are removed.