PO`d at salt mix

[gobytron]

If properly calibrated, your refractometer will be much more accurate every time.

I think IO advertises as 1/2 cup per gallon to get a 1.026 salinity.

If you're using good filtered water, you're readings shouldn't change that much.

If you use tapwater or your filter cartirdges are getting older, you will see some of the magnesium and other trace elements in the source water elevate your levels.

from the website

Q: After dissolving Instant Ocean® in purified water, my calcium and/or magnesium concentration seems lower than expected. Why?

A: Instant Ocean® is formulated to provide a solution with levels of calcium and magnesium found in natural seawater (NSW), assuming you use purified water to dissolve the sea salt. Tap water most often contains dissolved calcium, magnesium and other minerals that will add to the levels provided by Instant Ocean®. The specific gravity of NSW is typically 1.026 (35 parts per thousand, or ppt, salinity). When dissolved in pure water to a specific gravity of 1.026, Instant Ocean® should provide a solution that has 400 mg/L calcium ion and 1320 mg/L magnesium ion. If Instant Ocean® is dissolved to a lower specific gravity, then these concentrations (and, in fact, the concentration of every other ion) will be proportionately lower.