Effect of RODI Top Off Over Time

[tracemccune]

I am concerned that adding as much as 10% of my tank's water volume as RODI top off water weekly will result in the accumulation of some undesirable substances over the long haul. I do a 10% water change every week but adding back RODI water to make up for 10% evaporation loss makes me want to rethink allowing that much evaporation to take place. I monitor my RODI water for TDS and am good about replacing resin for my meter to read "0" TDS. But it seems like such a large amount of water to be continually adding that I am wondering what and how much accumulation of TDS (comprised of who knows what) is accumulating in a system that operates this way for a year, 5 years, 10 years, etc.

In your view am I chasing a minor issue, or is this something worth considering for the long term health of my corals?

 

[Randy Holmes-Farley]

While it is not impossible for RO/DI water to contain problematic ions, this concern is generally not significant if the effluent is 0-1 ppm TDS.

Seawater has more like 35,000 ppm TDS of various ions. A little bit more is not a concern, and in terms of alternatives, there really are not any that are always better.