Calcium question

[tobster]

I did the calcium, alkalinity test on my tank this afternoon and the calcium is showing at 350.
I used Red Sea test kit.
I then went and tested my premixed water that I mix in a 44g brute and found that the calcium is reading 330 in that.
Should I throw the remainder out that is already mixed? I use reef crystals by IO.
I only have 5 small corals in the tank. It’s a Red Sea 525XL 143 gallon.
When I tested a few weeks ago calcium was at 450.
Alk is also down from 7.0 to 5.9- also Red Sea test.

 

[Randy Holmes-Farley Verified Community Expert]

Might the salinity now be lower in both?

Maybe the kit is the issue.

 

[tobster]

Salinity is 34ppm

 

[Randy Holmes-Farley Verified Community Expert]

Salinity is 34ppm

How are you measuring it?

Calcium cannot drop that much unless you have been adding alkalinity.

 

[tobster]

I use a refractometer. I haven’t added or dosed anything.
I only checked it because my hammer coral was closed up most of the day and I thought there may be something wrong.
Could it be a bad batch of salt?

 

[Randy Holmes-Farley Verified Community Expert]

I use a refractometer. I haven’t added or dosed anything.
I only checked it because my hammer coral was closed up most of the day and I thought there may be something wrong.
Could it be a bad batch of salt?

Possible. Is this a new batch?

 

[tobster]

Possible. Is this a new batch?

Yes I just bought the 200 gallon box of IO a few weeks ago. This is the first bag out of the box.
Maybe completely unrelated but this morning my anthias fish has a bulging eye?

 

[Randy Holmes-Farley Verified Community Expert]

Yes I just bought the 200 gallon box of IO a few weeks ago. This is the first bag out of the box.
Maybe completely unrelated but this morning my anthias fish has a bulging eye?

Very unlikely to be the IO salt mix impacting the fish.