actaully your beneficial bacteria will be fine, ive used it as well as many others, its highly recommended by me and my lfs
(where i work) but the thing is it doesnt kill the stuff, it more of keeps it from coming back, so what youd wanna do is siphon out as much as possible, and then use the chemi clean.
Another thing to consider is it may not be phosphates, its gonna feed off of whatever it can in the tank as far as nutrients goes, trust me, the only thing you cna do is siphon it out when it gets bad, and maybe use chemi clean to help prevent its return,
i have jsut battled this and so many people come into the store with the problem, i also thought that phosphates were the problem, i got a kit and tested my tap and my tank, the tap had absolutely zero, and my tnak had minor minor traces of it, so the algea was living off of soemthing else.
The best advice i can give you is that your tank will go through this as well as many other blooms of algae, especially within the first year of set-up, so the key is not eliminating them but controlling them, since you will never totally rid your tank of every kind of algae. in about a year or so you will still ahve all these same things, but they will just balance out and when that happens it will seem like they are all gone, but they are there just balanced and wont seem as rampant HTH