Phosphates or Silicates slipping past TDS meter?

[jostafew]

Wow, thanks for the background, it's much appreciated! My current RODI system has a 10micron mechanical filter followed by a 5micron carbon block and a 1micron carbon. They were both changed a couple months back but in order to really squash this one I'll be starting with a fresh set top to bottom.

I'm going to pass your reply on to my wife; last year she read somewhere that Abbotsford has some of the best water in the lower mainland... I tried to tell her that compared to Langley where we were it is terrible. At one point last summer we could fill the tub and it would be noticeably colored, it's always tasted dirty, and my TDS meter indicates on average 10x the dissolved solids in the tap water. Despite all that she wouldn't let go of that article on water quality hahah.

[asylumdown]

Yah compared to Vancouver Metro, Abbotsford has some issues. I think you *can* have really good water, but it all depends on what mix and from what sources you're getting out of your tap at that particular moment. Obviously it's always safe for human consumption, but 'human safe' and 'reef safe' have different thresholds.

The 'legal limit' for nitrate contamination is 10ppm, but that's Nitrate reported as Nitrogen (a weird yet standard practice in water treatment and some areas of chemistry), which is actually closer to 44ppm nitrate reported as nitrate, which is how we talk about it in the hobby. The good news is that the average nitrate levels from the other two sources are both below 1ppm, and Abbotsford publishes a report indicating that they only get 5% of their water from the aquifer wells per year (none of which have nitrate levels acceptable for a tank), but that's an average for the whole system over a year. Moment to moment you never know what the mix is coming out of your taps.

Interestingly, the other element that routinely tests above the 'legal' limit coming out of the aquifer wells is manganese, which just so happens to be critical to oxygen evolution during photosynthesis. I haven't been able to find anything that showed elevated manganese encourages the growth of cyanobacteria (though I haven't looked all that hard), but people have been testing cyanobacterial mats as a zinc and manganese remediation technology because they're really good at sucking it up. Food for thought anyway.

Anyway I think you're on the right track, good luck!