How much did it cost?
Mild BGA issues are fairly easy to knock out without a blackout.
Especially if the conditions are good.
Simply do a good cleaning and pruning and stay on top of things for a couple of weeks often does the trick.
Neglect is something everyone does at some point and whipping a tank back into shape thereafter is something I've done many times.
Blackouts, EM, this etc,a re need only in intense cases.
But at least we know why the BGA and various algae shows up, no algicide will ever teach you that. Killing algae/BGA is not really the issue, there are many methods to kill algae and control it. And they are effective besides yet another algicidal product.
I think we have more than enough ways to kill algae, and too few worrying about growing the plants and seeing why we have the algae in the first place.
New folks see this and think that is the way to solve all their issues, well it's not and never will be.
I know you agree with me here and all, but if you are interested, I can give you a list of a dozen different things that will kill BGA..........