OMG - My SG is 1.030!

jpc763

jpc763

Active Member
So I have been using a Hydrometer since I set the tank up. Kept the SG between 1.023 and 1.026. Today it reads 1.025. Not bad.
Well Santa brought me a Refractometer. So after calibrating it using distilled water from Wally Mart, I measured the Salinity. 1.030

I know what I need to do to get it down, slow water changes with plain water (no salt). How much should I do, 10% per day?
Tank is a 55g with 70lbs LR and a 15g fuge.
Also, can Hydrometers be that crappy?
 
apos

apos

Member
Hydrometers can have all sorts of things wrong with them that throw them off: even tiny bubbles. They are basically nothing more than a balanced weight on a pivot, and that mechanical system can go wrong in all sorts of ways.
People's best bet with them is to periodically go to a good LFS and have them calibrate your hydrometer by testing it with water of known salinity (i.e. one tested with a refractometer). Since you already have a refract, you don't have to do this obviously...
But as far as I know, most refracts are calibrated via a special fluid of known salinity that comes with them. I didn't know they made units that could cal off of distilled water. I work at a place that calibrates radiation detectors, and to me, cal'ing something with a reference material that has 0 of the substance being measured sounds kind of bizarre. It'd be like bringing in a survey meter and calibrating it to detect radioactive material... without actually using any radioactive material. If that's really legit, then I wonder how it works.
 
D

dragonzim

Active Member
Originally Posted by Apos
Hydrometers can have all sorts of things wrong with them that throw them off: even tiny bubbles. They are basically nothing more than a balanced weight on a pivot, and that mechanical system can go wrong in all sorts of ways.
People's best bet with them is to periodically go to a good LFS and have them calibrate your hydrometer by testing it with water of known salinity (i.e. one tested with a refractometer). Since you already have a refract, you don't have to do this obviously...
But as far as I know, most refracts are calibrated via a special fluid of known salinity that comes with them. I didn't know they made units that could cal off of distilled water. I work at a place that calibrates radiation detectors, and to me, cal'ing something with a reference material that has 0 of the substance being measured sounds kind of bizarre. It'd be like bringing in a survey meter and calibrating it to detect radioactive material... without actually using any radioactive material. If that's really legit, then I wonder how it works.
Distilled water has a known salinity of zero which is why you can use it to calibrate a refractometer. The directions that mine came with specifically said to use distilled water, not a solution of any type.
To the OP - If all your fish and other inhabitants are living OK with the high salinity I would try and reduce it SLOWLY. Do a small change (1-2 gallons) a day with fresh RO water and bring the salinity down a little at a time so you dont stress out your inhabitants.
 
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