Salinity Measurement Suggestions

[sothoth]

I had a minor disaster about 2 months ago, when my floating hydrometer seemed to go haywire and started reading salinity wrong. It was saying I was in the middle of the "safe" zone, but my corals were suffering. I took a water sample to a LFS and they measured my salinity at 1.027!!

I bought two hydrometers, one is a high precision floating hydrometer, the other is a pin style. Here are links to similar ones:
Floater: http/www.drsfostersmith.com/product/prod...=2004&Nty=1
Pin:
http/www.drsfostersmith.com/product/prod...p;N=0&Nty=1

The floater initially agreed with what the LFS store said, and the pin style was very close. After 2 months of checking the salinity on both hydrometers every time, they're starting to diverge more and more, so the floater is saying 1.023 and the pin is saying 1.028. I tend to agree with the 1.023 floater reading but obviously that's tough to be sure about.

I was hoping for some input on what you all use to test salinity. I'm considering a refractometer and wonder if that's the way to go.

Thanks!

 

[SkiFletch]

Ah salinity measurement, so much fun aint it? Hydrometers WILL drift over time (usually they will read low when sg is actually high). Checking a hydrometer against a known standard should be done no less than every month and the hydrometer should be rinsed in fresh water after every use. Refractometers are a much more reliable source of salinity/sg measurement. They drift far less and you can always calibrate them yourself easily with RO water.

I still use a hydrometer (checked monthly by my LFS) but I keep my ear to the ground for a refractometer for sale locally. Great piece of hardware