Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Sounds like you've got some other treatments going.
But I wanted to mention something. You're correct that the Magnum's micron filter will not efficiently remove green water, though it should have removed at least some. However, if you "charge" it with diatomaceous earth, it will quickly remove 100% of green water.
Diatom powder is available at pool supply and hardware stores. I think I paid $8 for 20lbs. of it. Install the micron filter, add 1/2 cup of diatoms between the filter and the outer housing, add water, and give it a good shake just before turning it on. The diatoms will be sucked against the micron filter, coating it. Some will escape and produce a white cloud in the tank, but they'll soon be filtered out.
The diatom coating allows it to remove particles down to about 0.1 micron, instead of the 2-3 microns possible with the micron filter alone. The downside is that it'll clog faster, about 2-3 days is typical. But while it's operating, you will have the clearest water you've ever seen. I use it for green water, new installs with dusty substrate, or to rapidly clear detritus kicked up during heavy rescapes. Will clear virtually anything within an hour or two.