Hydrometer or Refractometer?

D

dannieboiz

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Jan 10, 2005
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Should I spend 10 bucks on a regular plastic hydrometer or just sehll out another 30 for a refractometer? Here's the spec of the refractometer I found... is this ok to use for aquarium? I have no clue on how to use one of these but heard they're more accurate. Used to just filling up the tube and watch the needles.... Are the ones that you can leave in the tank so that it'll float up and down as salt increase/rise?


RHS-10ATC (0-10% Salinity)

This model with high resolution scale of 1.0 PPT is developed for low concentration use. It can be used for measure the concentration of saltwater used in rinsing sea products or in cooking. Also, it can be used for aquarium water and seawater checks. The scale range of 1.000-1.070 Specific Gravity (SG) is provided. The RHS-10ATC has a built-in automatic temperature compensation system for field use.



Measuring Range: 0-100 PPT 1.000-1.070 SG

Resolution Factor: 1.0 PPT 0.001 SG
 
dannieboiz said:
Should I spend 10 bucks on a regular plastic hydrometer or just sehll out another 30 for a refractometer? Here's the spec of the refractometer I found... is this ok to use for aquarium? I have no clue on how to use one of these but heard they're more accurate. Used to just filling up the tube and watch the needles.... Are the ones that you can leave in the tank so that it'll float up and down as salt increase/rise?


RHS-10ATC (0-10% Salinity)

This model with high resolution scale of 1.0 PPT is developed for low concentration use. It can be used for measure the concentration of saltwater used in rinsing sea products or in cooking. Also, it can be used for aquarium water and seawater checks. The scale range of 1.000-1.070 Specific Gravity (SG) is provided. The RHS-10ATC has a built-in automatic temperature compensation system for field use.



Measuring Range: 0-100 PPT 1.000-1.070 SG

Resolution Factor: 1.0 PPT 0.001 SG
Click to expand...

Thats not a bad deal for the refractometer.Seems very accurate at part per trillion. What I like about those is how sleek they look.I feel like im james bond when im checking my salinity.
 
I looked at these. We use refractometers at work to check coolant concentration (BRIX scale). The thing I found dissappointing was that the accuracy is +/- .001 SG I do not know how that compares to a hydrometer, but that gives an accuracy range of .002 Isn't this too much for maintaining water quality as your salinity should not vary by more than .001 or 1 point either way? These things can be inaccurate that much. But I have never heard of a problem with them used for aquariums though.
 
I use a glass hydrometer that's accurate enough for my FO tank. One PPT???? THAT'S splitting hairs, folks. While I don't keep a reef, measuring salinity in PPT seems like an academic exercise. The OCEAN isn't that steady and constant.....................
 
My cheap floating arm hydrometer gives me a more precise reading, than my refractometer, but it is consistently off by 0.002 sg units (reads too low). My refractometer only has a precision of 0.001, but it has been calibrated so that I know it reflects the real salinity/specific gravity.

If we were talking about salinity (measured in ppt) 0.002 accuracy would be excessive, but the discussion is about specific gravity.
 
Look they can both be off BUT the difference is that a hydrometer can flux over time and start giving bad results, were as a refract is going to be off but its going to be off that .001 today or 1 year from now.I have heard of hydros being off as much as .005 before.
 
but it seems like the majority of the peoples are using a Hydro... I'll buy a refractometer if I run into another one. Cheapest so far was 50 bucks shipped.

On another subject... what kind of test kits are the easiest and gives best results for marine?
 
refrac vs hydrometer

One other thing to consider with refracs, i use them at work also (my fun job to calibrate them), and if they get a scratch on either the cover or the strip where you put your sample, they wont' work very well. Also if you drop it, (or kids play with it), they tend to not work also. Plastic hydrometer although not as cool looking, much more durable.
 
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