proper hydrometer readings

slukach

New member
If anyone can help, I really appreciate it.

I have a hydrometer that I use to test spec. grav/salinity. Sometimes I check it and things a perfect (1.023-1.024) and other times it will be above 1.030. I'll dump 1/8-1/4 gal of RO/DI in and check it later on and it will go back to normal params.

I have a 24 gal nano and don't really experience much evap. My tank temp ranges from 78.2-79.4 or right around there.

Is there some formula that I need to calc as far as water temp is concerned to get a more accurate reading on my hydrometer?

Thanks.
 

Randy Holmes-Farley

Reef Chemist
Premium Member
What type of hydrometer? What brand?

Swing arm hydrometers may not be especially accurate, but the do take temperature into account fairly well. Floating glass hydrometers are often more accurate, but need temperature corrections (detailed in link below).

You can make a DIY solution to test it:

Reef Aquarium Salinity: Homemade Calibration Standards
http://reefkeeping.com/issues/2004-06/rhf/index.htm

Temperature Corrections for Hydrometers
http://reefkeeping.com/issues/2004-07/rhf/index.htm

Specific Gravity Measurement
http://www.advancedaquarist.com/issues/jan2002/chemistry.htm
 

SeaView

New member
Randy. There is a script on this page for calculating SG factoring in temp and calibration temp. It is a wine making site but I believe the info is still acurate.

http://www.honeycreek.us/conversion.htm

Look for the table called: SG Temperature Conversion

Perhaps we could copy that script and post a link somewhere on RC.
 

Randy Holmes-Farley

Reef Chemist
Premium Member
It likely does not "understand" anything about seawater, so it cannot give a perfect correction, but it may be useful. For example, a 60 deg F hydrometer used at 86 deg F to read 1.023 should be corrected to 1.0271, but that calculator gives 1.0263. Not too far off, but not perfect.
 

slukach

New member
Its an instant ocean hydrometer (marineland labs) and it is a swing arm, I believe.

I tend to be super anal about my parameters (I would test pH, alk, ammonia, trate and trite everyday if I couldn't control myself). So when I see the hydrometer arm hitting the little piece of plastic that is put in to stop it when it gets past 1.032, I get really nervous.
 

slukach

New member
Thanks guys. I really appreciate the help. Also, thanks to Mr. Holmes-Farley. I am sure you are kept quite busy in here answering queries, and I appreciate your input and links.
 
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