Originally Posted by spedly (Post 992042)

So maybe fresh isn't the right word. I got the salt mix going two days ago and performed a water change yesterday. Salinity was measured at around 1.025. After the water change I turned off the mixing pump and heater so what I measured today was what was left at the bottom of the container.

I have a Vertex refractometer and ensure it's calibrated before every measurement. Do they have a limited lifespan? This one is about two years old.

You're right though something is weird. I thought that my old Red Sea test kit was garbage because of the low measurements. I've watched and re-watched YouTube videos on how to use the Hanna checker and I think I'm doing it right now. I'll watch it one more time....

I'm a little more concerned now that the Hanna checker is basically confirming things.

Originally Posted by spedly (Post 992053)

Wow...

So I did find an unused container of Pinpoint salinity calibration fluid. I used that to calibrate my refractometer and then checked the salinity of my display and fresh salt mix. Wow is it ever off. I'm measuring only about 1.021 salinity. That would explain why my calcium measurements are so off. Thanks for the tip Skimmer Juice.

Originally Posted by Myka (Post 992060)

That's exactly what I was getting at when I asked how you were calibrating. ;) I'm glad you found the issue.

Also, if your RO/DI isn't perfect, using it for the Hanna Calcium Checker will throw those numbers off too. I recommend using distilled water in the Calcium Checker.

Originally Posted by mrhasan (Post 992062)

Finger prints on the vials can throw off the numbers too. I used to handle those vials using napkins :razz:

Originally Posted by Myka (Post 992072)

Yes, so can using different sides of the vials (quartz thickness isn't always even). I always polish up the vials, and line them up in the checker the same direction every time. When I handle them to add reagents I don't touch anything except the lid and then the very bottom 1/2" of the vial (the test is taken about 1/3 of the way down the vial). They are fussy little things, but if used carefully they are very accurate. The Calcium Checker requires much more care to use properly. It's VERY easy to mess up that one. The alkalinity and phosphate/phosporus checkers are much more forgiving. I use them all the time, but the calcium one collects dust in my cabinet. :lol:

Originally Posted by Slick Fork (Post 992342)

So people seem happy with this?