Refactometer vs hydrometer

Bay Brony · Jan 1, 2014

Hi all
I just got a refractometer and calibrated it with RO/DI water .
I have been keeping my reef at 1.025 per an instant ocean hydrometer and I am very careful to remove all air bubbles, let it sit etc so I think it is a true reading.
My recently calibrated refractometer is reading at 1.021.
Can there be that big a difference? Could I have calibrated incorrectly? If so how do I go about increasing the salinity and how quickly? I am afraid to over salinate...
Thanks.

JMSKI333 · Jan 1, 2014

Hydrometers are pretty useless. I had the same problem when I switched to a refractometer.

My advice is to get 35ppt calibration fluid for your refractometer and throw your hygrometer in the trash.

Bay Brony · Jan 1, 2014

Could calibrating with RO water to 1.00 instead of the salinity solution cause it to be that off?; I am not sure if I should change anything or just wait to get the calibrating solution.

JMSKI333 · Jan 1, 2014

I have never calibrated with RO water before so I am not sure. If your tank doesn't appear to be in any sort of distress at this time then I wouldn't change anything and wait for the calibration fluid.

redfishbluefish · Jan 1, 2014

+1 with calibration fluid. You don't want to use RO/DI. Calibration fluid will be labeled at 53 mS and or 35 ppt.

Bay Brony · Jan 1, 2014

Yeah everything seems happy right now. Thanks a lot. Too bad I just placed a BRS order

JMSKI333 · Jan 1, 2014

Bay Brony said:
Yeah everything seems happy right now. Thanks a lot. Too bad I just placed a BRS order

\

Still get the calibration fluid and if you are indeed at 1.021 then I would slowly raise it to the desired salinity. (usually 1.024-10.26 for a reef)

Jlobes · Jan 1, 2014

definitely use the calibration solution. using RO water can lead to inaccurate results. Similar to a ph wand, when you calibrate, you want to use the two solutions closest to your target PH, or all three for best calibration.

I use a refractometer and check it with the calibration fluid, every time I do a water change. just to be safe.

sir bonkers · Jan 1, 2014

When I switched to a refractometer the reading on my hydrometer was 1.025 but my calibrated refractometer read 1.030. Threw my hydrometer away right then.

Bay Brony · Jan 1, 2014

Yes I wanted it at 1.025 which is why the refractometer reading is driving me nuts. But I just ordered the solution. Oh well I forgot to order my reef chili last time anyway

NC2WA · Jan 1, 2014

My advice is to get 35ppt calibration fluid for your refractometer and throw your hygrometer in the trash.

couldn't agree more...over time the arm to the hygrometer get stuck an readings are off.

Waters · Jan 2, 2014

I received a digital Milwaukee refractometer as a gift that is incredible accurate in a few seconds. I would never buy it myself due to the cost but I could not imagine going back to how I used to test with a cheap hydrometer.

cdness · Jan 2, 2014

Yeah you need the calibration fluid. The RODI water will never calibrate it correctly. You may be close, but for the livestock it is best to make sure with the correct stuff.

I do agree that the hydrometer is destined for the trash. Some people online swear by them, but they are inaccurate and can cause stability issues.

Mike J. · Jan 2, 2014

I'm one that swears by the hydrometer. I have an Instant Ocean one that's about 10 years old and some of the numbers are rubbed off. It's dead on with my calibrated refractometer. I actually checked my refractometer with the hydrometer once. The instructions with a refractometer say to calibrate it every time you use it.

revhtree · Jan 2, 2014

Hydrometers can be useful for quick measurements. Regular measurements should be taken by a refractometer IMO.

Jlobes · Jan 2, 2014

revhtree said:
Hydrometers can be useful for quick measurements. Regular measurements should be taken by a refractometer IMO.

come on rev...how much longer does the refractometer actually take!?

I guess it does take a bit longer than dipping a cup in the tank though.

atlorange · Jan 2, 2014

Do yourself a favor and get a digital refractometer. I use a Milwaukee, works great.

Jlobes · Jan 2, 2014

atlorange said:
Do yourself a favor and get a digital refractometer. I use a Milwaukee, works great.

whats the advantage over an analog version? aside from reading a digital number and needing batteries.

HoaglandDiver · Jan 2, 2014

dont forget, you can easily make your own calibration fluid. What I would like to see is a Refrac w/ a scale ONLY 32ppt - 38ppt. That would be MUCH easier to ready and MUCH more accurate. It's SO hard when you're dealing w/ a scale with distance between values of about 1/4the size of a millimeter to see exactly where your reading is. a 32 - 38 ppt scale could more easily be read.