I''m sorry that you got left out and feel this way!
I got diatom algae in my tank when I over ran the lighting time. The main ingredient that fuels diatom growth is Silicate and Phosphate. Although your testkit may say 0 ppm on Phosphate, I don't believe in it in every tank there is high amount of input of Phosphate, its in the food, when fish poop, if you run calcium reactor, etc. almost all photosynthetic animals utilize small traces of phosphate in their kelvin cycle. Thats where it gets neutralized ^^ if you don't have lot of corals, then high input of PO4, low out of PO4, you will get accumulation of PO4. Also Silicate is in tap water/deer part spring water etc, you need to use RO DI, more emphasis on DI, may be its time to change your cartridge also. Dripping Kalkwasser helps precipitate Silicate and PO4; also higher pH helps kill diatom algae, so drip Kalkwasser and less hrs on lighting.
Sincerely,