Jim I'll get you my tap TDS by tomorrow.

I would think even though there is, theoretically, little or no buffering capacity in the water after the RO it would tend towards a pH of 7 once the gas levels have equalized :huh. If the TDS is low wouldn't that mean the more pure the water would be? Also, is there normally any ions or molecules that pass through an RO membrane and must be taken out by DI?

I'll just let some sit out for a day or so or mix it up for a day or so to get the gas levels equalized in both water coming out or the DI and RO membrane.

All of this stuff is all an attempt to try and zero out nutrient sources giving my cyano a 7 course meal.