I have never had BBA in nearly 30 years of keeping aquariums. Recently I added a few Anubias from the LFS to my tank and suddenly I had a BBA problem. As suggested in many threads I used Flourish Excel at a normal dose 5ml per 10 galons to start 1ml per gallon each day since. It has been 4 days. Most of the BBA is gone and my pants are turning the best shade of green I have ever seen in my low light low tech planted aquarium. Why is this so effective?