I bought all three hanna checkers a few months ago. Alkalinity, calcium and phosphate.
the phosphate one is by far the best of the three and the most used. It's really nice to have a number just pop up on a screen and then you can track how the gfo
is working and when you need to replace the media.
The alkainity hanna is almost as good, it's spot on and soo much easier than dropping drops and figuring it out. lol It's like a 9 out of 10 only because i dont use it as frequently as I use the one for phosphates.
Now the calcium, test, well in my opinion is just a waste of money. I returned mine after a week to BRS cause it was so awful. It was beyond inaccurate, I even was on the phone with hanna trying to figure out a way to use it so it was reliable. They told me you have to use distilled water, not ro
water in the test sample and there were way too many steps in the testing procedure for me. lol
I paid like $45 or so for each of mine with a sale at BRS last year so to me it was worth every penny. In fact, gotta go check my phosphates now, almost forgot. lol I was at .23 a few days ago and just changed the media so we'll see where I'm at.