hmmm, I actually just noticed that you're in Abbotsford. Do you use RO/DI water?
The reason I ask is because the hydrogeology department at the UofC is down the hall from my office and I used their lab for a bunch of the soil testing I did for my thesis. I've become pretty good friends with one of the PhD students in the department and his whole project is on the very serious issue Abbotsford has with ground water contamination from agricultural activity. There's a gigantic aquifer that straddles the Canadian/US border that I'm pretty sure all of Abbotsford draws its drinking water from and at the highest levels of the aquifer (the top few metres) nitrate concentrations are truly insane. Drinking water is drawn from deeper down, but the nitrate plume extends all the way down just in decreasing concentration. Canadian regulations won't allow anything higher than 10ppm nitrate reported as N (AKA 44.5ish ppm nitrate, it's a dumb way to report concentrations) in drinking water, so I'm pretty sure Abbotsford has to bring in water from other sources to dilute the nitrate to within legal limits.
Because it straddles the border and so many American communities that are also drawing from the aquifer, there's a joint international task force presently trying to figure out how to deal with the problem (
http://www.env.gov.bc.ca/wsd/plan_pr...s/absumas.html). I'm not 100% clear on how municipal water supplies are directly affected by it, but if I lived in Abbotsford I'd definitely want to say very on top of my RO/DI maintenance as the levels of nitrate in your tap water are probably way higher than is acceptable for a reef tank, and also likely fluctuate a lot.
Just another avenue to explore anyway.