For us, one of the biggest benefits that ICP testing brought to the reefing hobby was not just the ability to test your aquarium’s saltwater, it was the ability to test the source water too, the pure, freshwater we use to make up synthetic salt mixes and to top-off evaporation. Reverse Osmosis and deionization are wonderful things and help us to produce our own source water for reef tanks, but they need monitoring too, and not just via a TDS meter.
Did you know that contaminants can slip through your RO/DI and into your tank even if you have a TDS of zero? And did you know that all DI resins are not the same? Even contaminants in the low parts per billion could build up to levels where they are toxic to corals and not via your salt, or your dosing regime, but through your top-off water. And this invisible build-up can lead to a slow decline.
Steve Visser from ICP Analysis.com explains more:
