what am I doing wrong with my refractometer/hydrometer

[Cheems]

Hello so I am currently trying to run hypo on my 75 gallon. I have been slowly lowering it and I bought a hydrometer to go along with my refractometer and my hydrometer is reading 1.016 while my refractometer is reading 1.013 and thats a dangerous difference. If my fish are off by 0.003 that could be dangerous during hypo and I dont know which one to trust. The refractometer ive had for around 3 months and the hydrometer I got today and is a coralife plastic swing arm hydrometer. I havent been the gentlest with my refractometer and ive been just wiping it off between uses so perhaps that might affect things? When I ordered the hydrometer I also ordered some 35 calibration fluid but it wont get here for quite a while. Thoughts/ideas?

 

[disaster999]

I would trust a refractometer over a hydrometer any time.

 

[vetteguy53081]

Refractometer likely more accurate and you sure calibrate it to assure best reading however use calibration solution and not ro water

 

[Js.Aqua.Project]

Most refractometers can be calibrated with RO water, put some RO on it and see if it is reading 1.000. If it is, trust the refractometer, if not then there should be a little screw that will let you adjust the calibration.

Edit/Update:

Some manufacturers prefer RO for calibration, some want a solution. RO calibration will work on all in a pinch but a solution may be more accurate.

 

[Gtinnel]

Essentially until tested against a solution with a know salinity you honestly can’t trust either one of them.
Calibrating with RO water is better than nothing, but generally it’s best to calibrate with a solution closer to the value you plan on testing. Although that may be somewhat negated by the fact that you are running hyposalinity.
If you have access to some cheap kitchen scales it’s easy to make your own solution with rodi water and table salt.

 

[Cheems]

Essentially until tested against a solution with a know salinity you honestly can’t trust either one of them.
Calibrating with RO water is better than nothing, but generally it’s best to calibrate with a solution closer to the value you plan on testing. Although that may be somewhat negated by the fact that you are running hyposalinity.
If you have access to some cheap kitchen scales it’s easy to make your own solution with rodi water and table salt.

hmm that may be possible. right now I know my refractometer is slightly off because with RODI water it measures slightly higher than 0.

Most refractometers can be calibrated with RO water, put some RO on it and see if it is reading 1.000. If it is, trust the refractometer, if not then there should be a little screw that will let you adjust the calibration.

Edit/Update:

Some manufacturers prefer RO for calibration, some want a solution. RO calibration will work on all in a pinch but a solution may be more accurate.

yeah what I may do is calibrate it with RODI water until the calibration solution comes in. does anyone know if this is safe enough to do or would it still be off and dangerous to trust for hyposalinity

 

[Js.Aqua.Project]

hmm that may be possible. right now I know my refractometer is slightly off because with RODI water it measures slightly higher than 0.

yeah what I may do is calibrate it with RODI water until the calibration solution comes in. does anyone know if this is safe enough to do or would it still be off and dangerous to trust for hyposalinity

Calibrating with RODI will be close enough to be trusted. I personally use RODI to calibrate and only use reference solutions to verify.

You don't have to order a solution, if you have a scale you can make one. @Randy Holmes-Farley has a simple one somewhere and a quick Google search should pull it up for you.

 

[Cheems]

Calibrating with RODI will be close enough to be trusted. I personally use RODI to calibrate and only use reference solutions to verify.

You don't have to order a solution, if you have a scale you can make one. @Randy Holmes-Farley has a simple one somewhere and a quick Google search should pull it up for you.

yeah but I already did order a solution. However it wont get here very soon so perhaps that would be quicker