53ms Calibration fluid for Refractometer

[pgordemer]

Anyone have any calibration fluid I can recheck my refractometer with at the meeting tomorrow?

 

[RichT]

I don't have any calibration fluid but I usually just check the ro/di. I'm sure someone will explain why that's wrong but if that is zero I feel comfortable it's pretty close.

 

[pgordemer]

You can do that, but many refractometers have a slope. Since your salinity test is going to be closer to 1.0264 then zero, it makes better sense to calibrate to 53ms/1.0264.

 

[mladencovic]

There was a lengthy thread when I asked the same question: http://www.njreefers.org/forums/index.php/topic,3600.msg33271.html#msg33271

Anyway, while not many people have calibration liquid, many have fine tuned and precise idea of their salinity so you can roughy calibrate on that. My was off by 0.3 !!! My old crusty hydrometer was actually more acurate then the new refractometer that now measures RO water as 0.97

Where are you, by the way?

 

[Carlo]

I've helped a few people calibrate their refractometers in the last couple of months from that thread. Most have "upgraded" from a floating hydrometer to the refractometer. I've asked them to bring both. Everyone's hydrometer has been pretty close to being on the money but the refractometers have been way off with 53ms solution after calibrating with RO/DI water.

It's a combined effect. If you don't have true ZERO TDS reading that can throw you off from the start. Also as Phyl mentioned the slope on many of them are pretty bad. 53ms calibration fluid is probably the cheapest thing you'll ever buy for your aquarium and I'd highly recommend it for anyone with a refractometer. I'd also mail order other test solutions if you plan on doing hypo using a refractometer or you'll again be way off and probably not be low enough to do hypo correctly to kill the parasites but that's off topic and another story.

Carlo

 

[pgordemer]

Where are you, by the way?

Paulsboro, NJ (10 minutes from Philadelphia