Caution for anyone using a refractometer

[fkshiu]

I've been happily using a Sybon refractometer for several years looking down my nose at hydrometer users. I used the "super pure" FRESHWATER reference solution that came with it to calibrate it a few times to zero.

I had read this Holmes-Farley article a while ago: http://reefkeeping.com/issues/2006-12/rhf/index.php#18. Today I finally got around to calibrating the refractometer using a proper SALTWATER calibration solution (http://www.americanmarineusa.com/acc...linity%20fluid).

I thought my SG was 1.026, but after calibration it was actually 1.0235! OK, not the end of the world, but it goes to show that any instrumentation you use is subject to error and must be properly recalibrated on a regular basis!

$5 got me pretty much a lifetime supply of the solution. A good investment methinks.