Refractometer measures salinity only?


Active member
Thanks for your time.

I'm about to perform a water change. My salinity seems alot higher than ussual. Its been 30-35 days since my last change - at which point my refractometer measured 1.026. Todays its closer to 1.028 or 1.029. My QT tank hasn't changed. I top off via a tunze osomulator.

I've been trying to raise my ALK lately by adding baking soda. I've added Alot. Is this impacting my SG? If I use salt mix to match the SG am I gonna be ok? Has the baking soda given me a false SG - is this even possible?
Adding alkalinity will change the SG a bit, but not enough to measure. The reading wont' be false, since the SG (and refractive index) is changing. I suspect you're seeing evaporation.

How much baking soda has been added?
Alot - Ive been working w/ Randy. I was dripping 5-6 teaspoons disolved in RODI a night into a total of 60 gallons of volume.
Oh, okay, sounds like a lot... I must have missed that thread, but as long as alkalinity isn't through the roof, you're probably fine.
I know this is a stupid question, but just to be sure...You aren't topping off with salt water, are you?