Looks like you have cyanobacteria, which is a photosynthetic bacteria (sorta like algae but not exactly since its not a plant). So much like others have stated, imbalance of nutrients, photoperiod, and water flow will help prevent it from continuing to be an issue.

Manual removal is going to be important, esp cleaning the substrate with a vacuum tube to get any excess organic matter out. If possible, add in extra flow through a water pump or increasing filtration. I’m not sure what your nutrient input is (whether you fertilize or potentially over feed) but that’s something to consider, usually the suggestion is whatever your tankmates will finish in like a minute or two and do a few feedings a day (unless you have just bottom feeders/shrimp then they wouldn’t finish food that quickly). And light wise, maybe reduce to 4 hours a day until it begins to clear up.

Bright side, because its cyanobacteria, it can also be taken care of with antibiotics like erythromycin, which should be safe for most tankmates, plants, and beneficial bacteria.