GW is one of the easier alga's to cure.
A UV will eradicate it in 1-3 days with little to no effort on your part and the tank will look awesome afterwards.
GW is VERY common with higher light PC/T5 lighting and it infest new tank set ups, tanks that have their substrate disturbed, have too many fish, get sunlight some part of the day etc.
Lots of light, lots of fish, little bacteria/new tank => NH4 + light= GW.
I've long suggested adding mulm to any new tank, not hard to get the dirt from another tank to seed yours.
Lots and lots of plants from day one, packing the tank will also accomplish no NH4 in the start up phase and no algae of any sort to speak of.
Zeolite and carbon are chemical methods to prevent new tank algae, NH4 etc also.
Water changes, like 2x week 50-80% also help for the first 1-2 months, again, for the same relatable reason: NH4.
With increasing light, new tanks and tanks in general require proportionally less NH4 to induce a GW bloom. Some tanks are very sensitive and get reinfected.
Poor CO2, substrate disturbing without following up with a water change that same day etc also will cause GW blooms in the previously infected tanks.
There are other ways to kill GW, maybe more than any other.
Chemicals are terrible at killing green water, stay away from these and in general.
Diatom/microfiltration works very well also.
Some have tried Willow branches, other's Daphnia, blackouts etc, these tend to work with milder cases. Water chaning the GW out never works if you have UV.
You may be able to water change + blackout for 5 days+ Excel dosing.
But the best results will be from a UV. See Ebay for a 30$ Via Aqua brand 5 w/unit, that's about all you'd need.
Regards,
Tom Barr