help! dueling hydrometers

[Amphiprion]

Refractometers/hydrometers are crap, unless they are calibrated. Last time I calibrated mine, it was off by .005 (had been calibrated 6 months previous). The water was really 1.030 but the refractometer said 1.025!

I agree. However, what you calibrate with really depends upon what you are measuring. For most brackish purposes, I'd calibrate with freshwater, since the range will be much closer to freshwater. If your brackish tank is on the upper end of the salinity spectrum, then it may be better to go with something like a seawater standard. Or, if you'd like, you can even make a "brackish water" standard, with some setpoint, like 15 ppt (which may be high for some tanks). That would be even more ideal. It'd be easy to do, since salinity is a linear relationship--so diluting a solution in half reduces salinity by half.

 

[robbob2112]

Just checked mine (came with a small bottle of "ultra pure water" and instructions to calibrate the zero point).. no adjustment required.

Have had it 2 years and checked it only twice before... never have had to adjust it.

 

[Pufferpunk]

There is a spceial calibration solution required.
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=18717

 

[xspainx69]

Refractometers/hydrometers are crap, unless they are calibrated. Last time I calibrated mine, it was off by .005 (had been calibrated 6 months previous). The water was really 1.030 but the refractometer said 1.025!

Well if thats so then.....:headshake2: Maybe im not really at 1.015 SG like Instant Ocean Hydrometer says HAHA

Maybe Im at like 1.020 Sg lol

 

[Pufferpunk]

I guess I'm more concerned about being exact for my reef tank, than my BW tank, which isn't as important what the exact SG is.

 

[brackeeper75]

Well if thats so then.....:headshake2: Maybe im not really at 1.015 SG like Instant Ocean Hydrometer says HAHA

Maybe Im at like 1.020 Sg lol

My IO Hydrometer usually reads high. I have my lfs use their refractomet and then i just adjust to what the hydrometer is reading. IHydrometer currently reads 1.030 however tests on the refractometer at 1.024 It's an easy temporary solution till i get a refractometer

 

[clsanchez77]

I will jump on this bandwagon as well. Refractometers are the only way to go as far as I am concerned. I purchased mine from Marine Depot for $45. As far as calibration goes, I calibrate mine using RO/DI water at the 0 point. I have heard of other people using calibration solutions or sea water standards. Quite frankly, the error from calibrating at the 0 point vs. the 1.026 point will mean an error smaller than what you can read on the meters (example +/-0.0005) at the other end of the spectrum. As Pufferpunk stated, its really more of an issue on reef tanks (almost an exact science) and much less of an issue with brackish tanks.

I am maintaining my brackish tank at 1.005 so I will continue to calibrate the 0 point with RO/DI water.

Chris