Just an FYI, Abbotsford gets its drinking water from 3 sources. Most of it comes from Norrish Creek and Cannell Lake, but at peak demand times they supplement the drinking water coming out of your pipes with water from the Abbotsford-Sumas Aquifer. A good friend of mine is presently doing his PhD on plumes of agricultural contamination in the Abbotsford-Sumas aquifer, and Abbotsford-Mission Water Services has published documentation acknowledging the nitrate problem with water from those wells. It's severe enough that they are unable to use some of their wells for years at a time because the levels are way over the legal limit for human consumption, and WAAAAAAAAAAAY over the acceptable limit for a reef tank. Abbotsford also adds chloramines to all the water from all three sources before sending it out in to the pipes.
An RO membrane won't do much to remove chloramines, it's the carbon stage that does that I'm pretty sure. I also think it will exhaust the carbon quite a bit faster than if it was processing water that did not have chloramines (I'm not sure if Metro Vancouver uses them, which is where Langley gets its water). Depending on when you changed your RO stages and how much water they've made since you've lived in Abbotsford, your RO unit may have been letting both chloramines and trace amounts of agricultural run-off in to the tank for months.
If I were you I'd get an RO unit with an extra carbon stage (or a chloramine specific stage if such a thing exists) before the RO membrane and start doing large water changes. I'd also nuke the existing cyanobacteria with a product like chemiclean as Denny suggested. People will tell you that cyano is the result of you adding too many nutrients, but what people don't realize is that cyanobacteria fixes nitrogen and carbon directly from the atmosphere (in fact it's one the most important nitrogen fixing organisms in all of evolutionary history), so you could stop feeding your tank for a month and the the cyano will actually continue to eutrophy the system all on its own. It certainly capitalizes on excess nutrients when available, but once it's established it can add organic matter and nutrients to your system just from metabolizing chemicals available in the air (plus a tiny bit of phosphate).
I have a working hypothesis that you'll never be able to get ahead of a nutrient problem with cyano present, as the cyano produces it as much as capitalizes on it, but that's for another thread...
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