What is the kelvin on the bulb, partition between the light and water-how old is the light bulb-How much natural light from what facing window (North, South, East, west) how long does it get the natural light and is any of it sun or is it diffused light.
How many and what species of plants and type of substrate-I am going to assume this is the 10 gal filtered tank...correct....
Where is the BGA-on plants, walls, floor...etc.....
You add ferts-what kind, how much and do you add them after a water change.....
More detailed info the better....you have to figure out the cause too-otherwise is can be an on-going problem.....
The way I take care of BGA-is with manual removal with a small siphon so that I can target remove the BGA and other organics without removing too much water at a time on a daily basis. Increase water movement and decrease natural light. If the light bulb is over or near 12 months of age- I change it to a new Daylight 6500k 20w for 10gal tank. Either remove the partition between the light/water or ensure it is clean and free of debris for best light penetration to plants. Depending on the species of plants-PP of 10-12h/day to help encourage plant growth. Best to add plant ferts after a water changes to remove any unused so the algae and BGA can't use it.
Can you post a pic....