GHA takes a lot of patience. Even if these products work for the type of algae you have it's still not going to be over night. There could still be more growth immediately after use. Pulling and patience is key no mater what route you go. GFO, carbon dosing, AlgaeFx, raising magnesium levels, pulling, ATS, etc. Combine them or use one at a time either way it all takes time.
I'm on my 3rd or 4th round of dealing with a tank wide algae out break. GFO and carbon dosing worked best for me before along with some pulling and doing the same again. Slowly and surely the algae is going away.
And remember if you use a particular product and the algae dies all it's doing is putting back into your system exactly what allowed it to grow in the first place. That's why pulling should still be done and possibly some other means of reducing nutrients like phosphates and nitrates. Also, if you don't change any habits or maintenance then after using a particular product that algae will just come right back with a vengeance as there's most likely dormant spores just waiting to come right back.