refractometer

Just picked up a refractometer on ebay (cost around 20 bucks) to check the accuracy of my swing arm hydrometer. Well, I had previously thought my DT was at 1.026....found out today that it was at 1.023! Huge difference! Guess I will slowly bring up the salinity. But I wanted to post this for those who are using a hydrometer....get a refractometer if you can!

 

Are you sure your refractometer is calibrated properly? They aren't infallible either, although more accurate they can still give wrong readings if they're miscalibrated.

Calibrate using something like this if you haven't.
PINPOINT® Salinity Calibration Fluid Bulk Reef Supply

 

agreed, they're not usually calibrated exactly out of the box - so just double check that and you're good to go!

 

I check my calibration pretty often and when I recieved it it was way off so as already said, check to be safe before changing salinity.

 

Yeah, I did calibrate it against RO/DI water. It had been off by a bit, but I corrected that.

 

Just FYI. RO water will not give you a precise calibration, the refractive index of pure water vs saline water will mean that your refractometer will be accurate at 0 but at 35 it will be off slightly because different liquids have different curves.

 

So what do you use to calibrate? It did not come with any calibration solutions.

 

I linked it in my first reply.

 

Thanks. I'll look into it.