You should use about 400mg 2 days in a row and do a 50% water change prior and after 3 days of treatment(4-5 days after the 1st pills).
Or you can do a 3 day black out which kills it as well.
However, the reason you got the BGA is not due to the traces, it was due to low KNO3 dosing after some point or lack of filter cleaning(which also reduces flow rates, also a cause/cure solution for BGA) etc.
Reset the tank with larger water changes and KNO3 dosing.
Keep up on dosing KNO3 thereafter.
It might take a few weeks to get things chugging along again, but the alga will go away if you keep up on things.
Regards,
Tom Barr.