Fishguy2727
Aquarium Advice Addict
- Joined
- Sep 24, 2010
- Messages
- 2,667
GH and KH together only tell you Ca, Mg, and carbonates. TDS is the conductivity of the water. Pure water will not conduct electricity. You want pure water for RO. Otherwise you may be adding phosphate, silicate, ammonia, nitrite, copper, iron, and many other things. If you are paying for RO you want to get what you are paying for. If you are getting GH and KH that high I don't think it is RO water.