Or supermarket drinking water...
I had problems with too much phosphate in tap water causing "green water" algal bloom...switched to supermarket spring water for my daily top-off and weekly 10% change (I buy 2.5 gallon containers of Springtime brand water). Threw in a phosphate absorber (Phos-X) and had clear phosphate free water in two days from the day...algal bloom dissapeared and I have crystal clear water now. The green hair algae will starve now I hope(I helped by manually removing as much as I could). For red algae I used Chemi-clean very successfully (It's been months since I killed it and it has not returned). My 10 gallon has been up since july. I do use Kent Marine Aquarium pH Buffer and add iodine (very sparsly), iron, and trace elements to the water.