Hydrometer- Child's toy or precise tool?
- Thread starter dodwyer
- Start date
Just get one from reefcentral from someone getting out of the hobby, or premium aquatics.com also has them, I think $20?
I don't like spending unnecessary money in this hobby, but I did get a refractometer even though I have a hydrometer from a tank buy. Easily one of the better decisions for my reef tank.
I don't like spending unnecessary money in this hobby, but I did get a refractometer even though I have a hydrometer from a tank buy. Easily one of the better decisions for my reef tank.
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- Nov 5, 2007
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cheap refractometers can give you a false sense of security. They need to be calibrated before each use. You get what you pay for. Usually a hydrometer is off but it can be consistantly off, so if you know weather it reads high or low, you can adjust for it. If you get the refractometer it's worth paying the extra for a good one, or you will need to check the calibration with every use.
don't buy a cheep refrctometer. there are too many things that can make them inaccurate, although precise,
firstly, you have to understand that refractometers do not measure salinity, they measure refractive index, there are many things that affect refractive index, most notably magnesium, which is a major component of NSW, in other words, you can have a refractive index that would suggest .35ppt, however if your MG is off, and it quite often is, that will not be your salinity.
also, always use .35ppt calibration solution, I do not care what the instructions say, don't trust zeroing with RO/DI for calibration... to do that you are assuming the correct slope in your prism...and that's a very big assumption
always buy a refractometer with temperature compensation and always wait 1 minute before taking a reading, temperature differentials play havoc with refractive indexes
firstly, you have to understand that refractometers do not measure salinity, they measure refractive index, there are many things that affect refractive index, most notably magnesium, which is a major component of NSW, in other words, you can have a refractive index that would suggest .35ppt, however if your MG is off, and it quite often is, that will not be your salinity.
also, always use .35ppt calibration solution, I do not care what the instructions say, don't trust zeroing with RO/DI for calibration... to do that you are assuming the correct slope in your prism...and that's a very big assumption
always buy a refractometer with temperature compensation and always wait 1 minute before taking a reading, temperature differentials play havoc with refractive indexes
