Low-ish Ca with freshly mixed salt

[Barry_Cuda]

I'm trying to set a consistent baseline for alk/Ca/Mg in my tank, and I'm finding that my freshly mixed saltwater (using Instant Ocean) tests out to 385 ppm Ca. This seems kinda low to me. Wondering if it makes sense to switch to a different salt, or if I should just plan to maintain Ca around 400 via dosing and expect water changes to lower it a bit. Thoughts?

 

[RobZilla04]

What was the salinity/SG of the tested water? What test kit did you use for Cal?

All of the hobby grade kits have a margin of error as well as the human element. Actual Cal could be above 400 and test to 385.

 

[Barry_Cuda]

I'm using a Salifert kit. My refractometer shows SG right at 1.026.