I wanted to try Tom Barr's method of "don't touch for 3 weeks" for GDA but I didn't stand viewing my tank after 1 week of no cleaning.
I tried another method:
1) Turned off filter.
2) Cleaned glass, plants and decoratives that had GDA, leaving the dust into the water column (equipment that could be removed, scrubbed with a sponge and brush and rinsed in tap water to remove spores).
3) Miserable plants that couldn't be cleaned, found their way to rubbish.
4) Performed 75-80% water change (100% r/o as always).
5) Cleaned filter's sponges and changed filter wool.
6) Connected uv sterilizer.
7) Dosed 1.5X the Excel water change dose
Tomorrow I will buy Seachem clarity, to help clump the algae particles together big enough so the filter wool could take it out. Also planning to do:
1) Tank wiping every day for at least 3-4 days, changing 75-80% of the water and dose the same Excel I dosed today after every w/c.
2) Clean the filter's sponges every 12 hours and use clarity after this.
Hope it will go away, I think it's a very effective method, so fingers crossed.
Here is the tank after a big trim: