View Full Version : Recommended Hydrometer

11-14-2005, 07:44 PM
Are all hydrometers the same? Is there a favorite among reef aquarists?

11-14-2005, 07:56 PM
Yeah there all the same, inaccurate.
Spend the extra $$ and get a refractometer.

11-14-2005, 07:57 PM
most are crap. buy a refractometer and you will be happy.


11-14-2005, 09:00 PM
An inaccurate hydrometer can lead to a tank crash if your salinity is off by too much or for too long. Learn from the experience of others & get a good refractometer as suggested by the others. It'll save you money & head aches in the long run.

11-14-2005, 09:15 PM
I was using a hydrometer thought everything was fine then one day I got n awesome deal on a refractometer and when I tested my water I was off by .003 which is alot...I thought I was at 1.026 when I was actually at 1.023......I was glad I was keeping my salinity high or I could have lost alot of fish! And inverts and corals

11-14-2005, 10:06 PM
If I can remember this right, most Hydrometers are calibrated for 60 degrees f. Cold water has a higher density than warm water, and that works out to ~.001 difference per 10df. In other words, for most hydrometers, if you're measuring 1.0023, a refrac would put that at ~1.0025. This leads many people to say "WHOA!" when they see their results from a refrac, and assume that their hydrometer was bad. Not always true.

When we tested our hydrometer against a calibrated refrac, we were .003 out (so, .001 adjusted). It was very consistent over multiple tests, on various sources, so we now trust our hydrometer (and make the necessary adjustment). Not perfect, but close enough for jazz.

On the other hand, many people note that the refractometers are now so cheap, why not buy one? Not bad advice at all.


11-14-2005, 10:36 PM
Ok a refractometer it is. Any brand better than the others? Approx. how much do they cost?

11-14-2005, 11:11 PM
sybon seems to be the market leader. they are around 65 bucks at j@l or oa.

11-18-2005, 12:50 AM
Bought Sybon refractometer from OA and it works great. Thanks for the advice.

11-19-2005, 04:03 PM
I have an Instant Ocean hydrometer, and a refractometer. The hydrometer is a lot more convenient to use. I use the refractometer on occasion to check hydrometer accuracy.

11-19-2005, 04:45 PM
Does anyone find any drift between the hydrometer and refractometer or is the error consistent?

11-19-2005, 04:46 PM
I have a reading of about 1.025 hydrometer with tank temp of 80.5 F with lights on and 79.1 lights out
so what does this work out to based on the calibration and a refract.

11-19-2005, 05:45 PM
When we tested a friend's hydrometers, they were all off by quite a bit so it's hard to say without a straight comparison using both instruments how to calibrate your hydrometer. If you don't want to buy a refracto for now, best bet may be to borrow one from a friend & calibrate your hydrometer at home.