I've been using RO filters for many years. It's the only way to remove copper from the water I put in my reef aquarium. :thumbsup: When I started this first grow I'm in, I used that!

I bought both of my RO filters on e-bay. I used the first for a couple years. In that time the cost for the filter dropped a lot. They now had clear filters making it easier to judge when to replace filters. I discovered phosphate was causing my algae issues in the tank about the same time. So, instead of just replacing my cartridges. I bought an entire new 4 stage with DI. Then tied my old filter minus the membrane cartridge to the input of the new one. NOW I use a 6 stage (two prefilters, two carbon blocks, then the membrane, then through the DI cartridge. Water is about 1TDS before nutes!