Holy crap! I have been using 170ppm TDS water!

[deepRED]

I feel the same way about the waste water with an ro unit. I ran ro/di for years but when I moved I got lazy and didn't set it back up and used conditioned tap water.

Mind you my tds out the tap is around 8, but like Brad mentioned, it's an insurance policy.

I know a lot of people in BC with small to medium tanks use the aquarium pharmaceuticals tap water filters. For many out here this is enough to get their tds down to zero.

Not really cost effective if you are running larger systems though as the cartridges can get pricey.