Anyone using Aquaforest Reef Salt ever measure calcium of fresh salt water? I just received a Hanna checker for calcium the other day and this morning I decided to measure it - it came out to 474. Is that consistent with other people's measurements?

420 my last check

Mine was something between 420-440. Cant remember precisely.

I don't like the Hanna Calcium checker -it always reads about 50 ppm higher than Salifert and Elos when I used it.

*grumble*

Really? I was using a Red Sea test kit and it was waaaay off. I was measuring ~360 in my display so I started dosing kalk to bring it up. I could never get it higher than 380 - which I thought was weird. I tested the display yesterday and it was around 490 which was when I realized my Red Sea kit was out to lunch. I was expecting the Hanna checker to be a silver bullet.

Doh! I think I've been messing up on my testing procedures. I'll perform another test tomorrow and see what comes out of it.

So I properly tested some salt mix I made yesterday and it tested 353. This is more aligned with the test results I've been getting all along but certainly different than the results others are getting. Might be time to try a different salt mix.

If you're getting 353 ppm calcium in freshly mixed Aquaforest salt then I think you're making errors testing or maybe your refractometer isn't calibrated and the specific gravity is a lot lower than you think it is.

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.

You calibrate it every time before you use it? That's a bit excessive. If you're just using it on one or two tanks, and it's not traveling around anywhere getting bumped around or exposed to significant temperature changes, then once every 2-3 months should be sufficient. How are you calibrating?