Trapper,

Nick's advice is right in line with effective management of GW.
You can correct the plant nutrient issues etc, but.........
You still need to remove the GW adults that are growing.
They are much tougher and able to withstand any abuses you throw at
them.
GW spores need the NH4 to get started. But if there's not enough ?NH4
tio be and, you'll never see GW, no matter what the NO3, PO4 level
might in th eupper ranges(Eg 2ppm PO4/NO3 at 75ppm).

So I gave several methods to kill and remove the GW.
Pick one, try it, if it does not work, try another one.
I like UV because I had one laying around from years ago and it's very
easy to flip a switch and kill it in a few hours and never have it
come back again.

So I started dosing NH4 to see what caused GW. It was easy to do since
the removal process was simple.
I dosed plenty of NO3 and PO4(but no NH4), I could never produce the
GW bloom.
High traces, lots of light lots of CO2 etc.
Only the NH4 and urea(which turns to NH4 very fast in water) caused
the bloom.

Once you get rid of it, take care of the plants and you'll likely
never see it again.
But you need to remove what's there.Water changes seldom do the trick
except in mild cases/low light tanks.

Regards,
Tom Barr