Low phosphate even though dosing plenty, green spot algae on stem plants
I rescaped my tank and changed the substrate to ADA ammazonia about 6 weeks ago. The plants are doing good so far with the stem plants however, covering in green spot algae. I am dosing plenty of ferts 3 times a week, using a all in one dry fertilizer. This fertilizer should rise my phosphate by 1.3ppm for 12ml for 100litres, my tank being 290litres this should give me roughly 12ppm per week. In my old setup my phosphate was always indicating at least 5ppm, however now its only indicating very low ammounts even straight after dosing. I read that the ada soil absorbs the phosphates, what is behind this?
I don't think its my lights or co2, ph at 5.95 kh at 2, gh normally at 4 raised to 8 with epsom salt as my tapwater already has 20ppm of calcium, so good ratio here too.
I previously had a lot of green spot algae on the drift wood too which is now completly gone, thinking this was normal, at the same height as the stem plants, however plants still affected.
Any advice appreciated.