Edited: Tom's right on the W/C's I forgot about the rebound affect. Old habits die hard ! My Bad !!!

Double dose Excel. SAE's and Amano shrimp would help, but until you go to Co2 this will be a re-occuring scenario. You could lower the light, and dose religeously W/ Excel for the short term.

The thing is, if I see BBA I know I can simply increase Co2, and watch it melt away in a matter of days. You can do that W/ Tanked Co2 ! If You don't want to go to Co2 then simply decrease the light.

What is your W/C routine ? What is your light cycle ? and Yes I'm Paul Parroting George, he's right of course. Good Luck, Prof M