That is actually Cyanobacteria. The best and quickest way to rid your tank of it is to treat the tank with Erythromycin. A 5 day treatment will kill it. Prior to treatment you need to vacuum as much out of the tank as possible and on day 6 after your 5 day treatment do a large WC
. Erythromycin won't harm BB but can cause a ammonia spike due to the dying bacteria if there is a lot of it.