Not to burst any bubbles here but you may want to find another test kit other than Hagen. A recent example showed me that Hagens Ca test kit read much higher than is actually in most tanks. Thsi also varies from test kit to test kit but more so with Hagens.
A friend and I recently decided to test our water using his Hagen and my Aquarium Pharms. Both readings were from the same tank. His read 560 ppm (Hagen) and mine read right at 500.
He purchased a newer test kit and got a reading of 520 versus again my result of 500. To see if it was my test kit I purchased a new one as well. Again mine read 500. Using my sisters test kit (Salifert) he got a reading of 500.
Whether it could be attributed to the age of the initial test kit is arguable. The newest test kit of the same brand still gave a much higher reading than either the salifert or the Aquarium pharms. All the other tests using the Hagen Master kit were identical to the Aquarium pharms master test kit. The only test we didn't compare was the Alk because I needed a refill at the time. One of the tests not included in the Aquarium Pharms master test kit

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Not quite scientific perhaps but somewhat conclusive in repitition.