Hydrometer vs Refractometer

[Red Deer Reptiles]

yes you can use ro water to calibrate remember ro water is at 0 so look in your refractometer if its not at zero adjust the screw to bring it to 0 been doing for 10 years.dan

[Red Deer Reptiles]

we suggest in the future have the store where you buy your refractometer calibrate it for you hope this helps.dan

[JDigital]

Your refracto should have come with calibration fluid, I got mine at Red Coral too, same one, and mine came with it.

[new but handy]

I've got the Sybon refractometer it came with a bottle of ultra pure water for calibration (water-- 0% anything +/- o.o1ppt) It's actually called "ultrapurewater"!
It seems to do the trick, although I've never tested it against anything else

[Hairytank]

Yes, I used the "ultrapure" water to check the calibration and it was right on the money. So, if that (0.0129) is an acurate reading, which I think it is, then I will do some slow changes to the water.

[mark]

seen this poll?

http://216.187.96.54/vbulletin/showt...=Refractometer

[mike31154]

I have 3 hydrometers and 1 refractometer. One of the 3 hydros is the type you float in water and the other two are swing arm types. All 3 hydros came with used tanks that I purchased. The 'float in water' hydrometer appears to be more accurate than the two swing arm types and reads favourably when compared to the refractometer. In addition the float hydro has a built in thermometer. One thing to remember about hydrometers is they are not temperature compensated and since they are initially calibrated to read at a certain temperature, if you don't compensate, you will get inaccurate readings. Most refractometers are automatically temperature compensated, you just need to wait a few moments for the fluid to get to the same temperature as the refractometer glass.

I've seen on other boards that some folks recommend calibrating refractometers using a fluid (pinpoint usually) which is at 1.026 specific gravity. The reasoning being that this is where you want your refractometer to be most accurate and if you calibrate at zero, it's not a guarantee that it is accurate at the salinity range we usually check. I asked the question on that board if anyone had calibrated using the 1.026 fluid and then checked the zero with pure water to see if there was any error and never did get a satisfactory response. Personally, I calibrate at zero and have even found that it's almost impossible to see a difference at zero whether I use Vernon tap water or distilled water.

Since getting the refracto, I keep my water at around 1.024 on the refracto scale. I don't worry too much about a point or two difference. But I do make sure that when I perform a water change, the new water is as close as possible to the tank water. I check it two or three times to make sure since I tend to change a lot of water every 20 days or so vice smaller changes more frequently. Other than my fish, cuc, I have an anemone and a number of soft corals as well as a hammer and all the livestock seems fine with this level of salinity.

[fragNplug]

After reading this i guess its time to get one myself, im scared at what mine really is now.

[Johnny Reefer]

I have both, but haven't used the hydrometer in about 3 years. I always use the refractometer and will continue to do so. But a question comes to mind....if the error of a hydrometer is known, could the hydrometer not still be used and just simply apply the error in calculating the true reading?...or is an error in a hydrometer prone to fluctuate? (This is assuming the instrument is cleaned thoroughly after each use).

Cheers,

[Red Coral Aquariums]

A refractometer is possibly the most important initial piece of testing equipment you can purchase.
We have sold many hydrometers but always recommend the refractometer.

I have found that only approx. 5% of new hydrometers are accurate but once you find out how much they are off they (under proper usage) remain consistent. We test hydrometers going out of our store and they are an average of .04 out but have had numbers of .1.

Kevin