Refractometer Question/Problem

[Charlie]

I am trying to get a pail of water with SG of 1.035-1.040.

My hydrometer gauge peaks out at 1.030 and that is the reading that I get with the hydrometer. The hydrometer reads 1.023 on my cycling tank water. Both samples are at 79deg.

Here is the problem: I bought a refractometer from liveaquarium.com and assumed it was deadly accurate.

When I tested the tank water it reads 1.025 exactly.
When I test the pail of water it also reads 1.025 exactly.

I carefully wiped the lens with clean tap water and then dried it with a soft cloth beyween tests. I repeated the above senario several times with both water sources getting noticably different reading when tested with the hydrometer and getting the exact same reading when tested with the refractometer.

WHAT IS UP WITH THIS???????????

 

[roka64]

Did you calibrate it with distilled water first? There are instructions in the plastic box that explains how to calibrate it. Different reading can depend of the temp of the water too.....

 

[Charlie]

When checked, it calibrated to ZERO when tested with Poland Spring water. The food store didn't have "distilled water" but Ill try the drug store today.

Even if the reading is inaccurate, I can't understand how the refractometer could give the same reading for two samples of water that appear to be quite different in SG.

I will recalibrate with distilled water but it doesn't seem like this will resolve the discrepancy.

 

[roka64]

It's this one:
http://www.drsfostersmith.com/Produ...fractometers&ref=3969&subref=AA&N=2004+113761

I found my hydrometer to be off by .00500, my hydro was testing 1.022 and refracto was actually 1.027.
How are you measuring, are you leaving the hydro in the water, is there water movement? That can cause the swing arm to move and give you inaccurate readings. I would have to say, if you calibrated correctly, you should have very accurate readings with the refracto. Also, I am not sure if spring water is "pure" water like distilled, that might be throwing off the calibration.

On a side note, when you get distilled water, put it in your hydro and see what reading you get.....

 

[Charlie]

roka64,

You are correct about the model I bought from liveaquaria.com. The same refractometer costs $99 @ my LFS.

I went to 6 places, including the auto parts store, before finding some distilled water at the CVS drug store.

I'll recalibrate it tomorrow with the distilled water but I'm betting the the problem won't change. We'll see.

Using the hydrometer, I submerged the unit and moved it back and forth a bit to dislodge any air bubbles. Then I raised it out of the water and placed it on a flat surface. Excess water automatically drains off. Swing arm settles pretty quickly. The hydrometer seems to work well. It may, or may not, be accurate but it is responsive to changes. The refractometer does not seem responsive.

I'll post an update when I recalibrate the refractometer in the morning. My tanks are at the office and I done for the day. Hopefully, all of my LR should arrive tomorrow and the dip pail will be ready.

 

[Charlie]

UPDATE

I recalibrated the refractometer with the "distilled water". However, it calibrated right at zero without any adjustment. Exactly the same as the Poland Springs water.

My office generates several gallons of water each day from the two dehumidifiers that are running around the clock. Does this collected water have any use to the aquarist? Is it mineral and/or contaminant free?

 

[austinsdad]

My guess is that it pulls not only moisture, but other room contaminants with it. I'd stay away from it, but thats only a guess.

 

[roka64]

Hmm, not sure about the calibration. Did you try the distilled water in your hydro? You can kind of calibrate it by marking where the arm stops as 0.