[Kathyy]

I haven't ever seen it suggested that BBA prefers lower light, always that too much light and not enough CO2 encourage it.

I would raise your fixture to 12" above the tank and run the lights for 6-8 hours a day. If your plants falter at 6 hours then increase the day length. Or turn off a bulb and leave at 4" above the tank. Or put a layer of shade, aka common fiberglass window screening, on top of the tank.

Poor water circulation means all plants don't have equal access to nutrients, might consider increasing flow in the tank to about 10x by adding a power head. Fish can handle more CO2 in the water if there is also a lot of O2 so be sure there is a good ripple on the water's surface.

Is your filter in good shape? A healthy biological filter helps fight algae somehow and keeping debris removed, not just in the filter, keeps organics down. How much and often are your water changes? I came home to a terrific mess in my tank after a couple water changes were missed while I was on vacation.

Pick out BBA off hard scape and equipment and remove infested leaves. How much Excel are you using? Try doing 2x the usual dose when water is low during a water change, squirt of the stuff you cannot remove manually, let the tank cook for 20 minutes then fill the tank.

You may always have a few tufts forming on old and damaged leaves week by week. We are gardeners and need to tidy up regularly. It is the unstoppable situation that isn't acceptable!

 

[Kathyy]

I know, my plants are far happier with 8 hours of light. You can only go so low before you are hurting the plants trying to reduce light enough to discourage algae! P. Kawagoeanum went from 6" of small leaved healthy growth to 12" with giant leaves when I increased the lighting! Either that or increased magnesium. Why my tank needs more Mg I don't know but it sure helps.

How are the plants growing? Happy plants don't collect a lot of algae.

EI calls for 50% water changes unless you are feeding a reduced amount.

I would definitely go back to targeting problem plants and picking off damaged leaves. There is no point trying to save stem, crypt and java fern leaves but Anubias leaves usually do okay after BBA is dead. Don't have any sword plants, suspect it would be best to remove any infested leaves.