Anyone use the Hanna instruments testers for their calcium and alk? I've been using the API test kits since I got into the hobby about a year ago but recently decided to give the Hanna s a try . My alk test seems to b ok . It's pretty consistent as I check alk daily . But for some reason the calcium test is all over the place. For starts it's read over 100 ppm more than my API kit and it's really inconsistent . I've did several tests back to back , making sure to do then exactly the same , and it's still all over the place . Anyone else have this issue ?