I have been using MSU fertilizer for reverse osmosis water but it also comes for well water. My well water was too high in salts so i put in the RO system. I use the same fertilizer year round because it hurts my head to remember what 500 orchids want. I fertilize every three weeks but I may switch to 2 weeks in summer. That's how I adjust, by how often. But don't go by me.
