I decided to try something new :-) Instead of everyday water changes and fuss I decided to introduce LOTS of floating plants, almost covering all the water surface. I got Salvinia natans floating plant.
Since "green water algae" thrive in water with NH4 and strong lights, I planned to add floating plants to shade the tank (something like black-out) and to uptake the NH4 from the water column.
I also started dosing Easy Life FFM (fluid filter medium) in USA aka Easy Neo. This fluid product has a very good CEC (cation exchange capacity) and is able to bind NH4 very fast. I dosed Easy Life FFM every second day (recommended is once a month).
This next photo was taken approx 10 days after I had introduced the floating plants and Easy Life. Amazing!! And I didn't do any water change at all !!