Refractometer vs hydrometer

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loganj

Aquarium Advice Addict
Joined
Oct 25, 2002
Messages
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Location
Chatsworth, GA
I recently ordered a refractometer from Tim Crowley on ebay (moneyreapertc is his ebay user name) for $45 including shipping and ins. It arrived today. Seems to be a good one so if anyone is interested in buying one of these, you might contact this guy.
Anyway, after calibrating it, I compared the readings of my two hydrometers with the refractometer.
Coral tanks #1 and #2
Deep 6: 1.0255
Seatest: 1.026
Refrac: 1.027

20g reef
Deep 6: 1.025
Seatest: 1.0255
Refrac: 1.0265

5 gal bucket of SW that has been sitting in the corner for about a week.
Deep 6: 1.028
Seatest: 1.029
Refrac: 1.030

I was surprised at how close the readings were. I have seen the Seatest and the Deep 6 vary as much as .002 SG. I also have another Seatest laying about somewhere that always reads about .001 lower than the other Seatest. I guess this is, although not very scientific, evidence that the swing type hydrometers are close enough for our purposes. I think the refrac was worth the money though...I like the precision that it offers. Perhaps the best thing to do is get your hydrometer checked against either a refractometer, salinity meter, or water with a known salt content. Then you have a correction factor if needed.
 
When I got my refrac I also checked it against my Deepsix. The Deepsix was only .001 SG's off from the refrac. I guess for $10, that is pretty good accuracy for a swing arm.

I love my refrac as well. So easy to use.
 
i was actually thinking last night why someone doesnt make an intank hydrometer that you can just look at and see your salinity instead of always dunking something in the water.
 
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