It does look filamentous like lyngbya. Either way both are products of nutrient limitation or one nutrient suppressing the other.
We are past ammonia at this point. Though having none is a good sign. Po4 testing would help here.
As others stated, manual removal is best. You can try the no water change and increased feedings for a month. I wouldn't exceed feeding twice a day as it can hurt water quality but a build up of detritus can help increase P and the fish can increase N.
Otherwise, stick to weekly or biweekly water changes as you have been, reduced to 10% and start dosing potassium phosphate(seachem flourish phosphorus) and sodium nitrate(purchased from amazon). You don't need to go buck wild on dosing. Maintaining phosphates around 0.02-0.08 and nitrates between 2-10ppm. Remember, what you dose needs to be tested.