Extreme salinity difference

[ReeferHolland]

Hi all, I have some confusion with measuring salinity. I started a month ago with cycling my tank with a salinity of 1.025 measured with an aquamedic LED refractometer.
Last week I found out about the tropic-marin hydrometer so today I bought it for faster salinity measuring. But here's the problem, the difference between the hydrometer and refractometer is 5 points. The hydrometer reads 1.020 at a temperature of 25°C / 77F
I also use tropic-marin pro reef salt.
The other problem is that I yesterday quarantined my first 2 clownfish but I don't know what the actual salinity is now.
Any tips?

 

[Daenion]

That is not a good position to be in but there are couple things you can do to verify.

If you make your own RODI I would use that to check the refractometer or better yet the calibration fluid it should have come with.

Checking the hydrometer is harder since you need to have enough water with known salinity.

I have milwaukee and hydrometer and would trust the hydrometer over anything else if the beaker is clean and you are giving it enough time to settle.

 

[ReeferHolland]

That is not a good position to be in but there are couple things you can do to verify.

If you make your own RODI I would use that to check the refractometer or better yet the calibration fluid it should have come with.

Checking the hydrometer is harder since you need to have enough water with known salinity.

I have milwaukee and hydrometer and would trust the hydrometer over anything else if the beaker is clean and you are giving it enough time to settle.

I did calibrate it multiple times with calibration fluid. My own RODI also shows exactly 0 after that. So now I'm not sure about both of them. Maybe I go back to my LFS to compare it to their hydrometers and refractometers

 

[RFGuy_KCCO]

I trust my T-M hydrometer over both my Milwaukee salinity tester and my refractometer. All three usually match, but if there is a discrepancy, I go with the hydrometer reading. I would do the same if I were you.

If I had to guess (and I do), my bet would be on your calibration fluid being off a bit. Try another brand or batch.

 

[Daenion]

I did calibrate it multiple times with calibration fluid. My own RODI also shows exactly 0 after that. So now I'm not sure about both of them. Maybe I go back to my LFS to compare it to their hydrometers and refractometers

It is very hard for hydrometer to be wrong unless it has a manufacturing defect then you can probably exchange it.

I personally never liked the refractometers that you have to read yourself. I presumed I would make a lot of mistakes with that.

 

[ReeferHolland]

I trust my T-M hydrometer over both my Milwaukee salinity tester and my refractometer. All three usually match, but if there is a discrepancy, I go with the hydrometer reading. I would do the same if I were you.

If I had to guess (and I do), my bet would be on your calibration fluid being off a bit. Try another brand or batch.

My calibration fluid is just 0 salinity water. Its not the 35ppm fluid. Both calibration fluid and RODI water read 0.
Thanks for the advice, I will trust on my hydrometer for now. But will compare it to another or more hydrometers from TM for confirmation.

 

[ReeferHolland]

It is very hard for hydrometer to be wrong unless it has a manufacturing defect then you can probably exchange it.

I personally never liked the refractometers that you have to read yourself. I presumed I would make a lot of mistakes with that.

Yeah me too, thats why I bought the hydrometer. But now it probably turned out my refractometer was off with 5 points so thats a problem I guess

 

[ZoWhat]

Refractometer with lab grade 35ppm salinity calibration fluid

 

[ReeferHolland]

Refractometer with lab grade 35ppm salinity calibration fluid

I will try that too

 

[mdb_talon]

Agree with most that a hydrometer is usually the safest thing to trust. They generally just always work and unlike other means of testing no calibration needed. If they are clean and no air bubbles attached they will always give consisten measurements.

Having said that though if there was an issue in manufacturing and poor QC then maybe it can be wrong(though at least it will be consistently wrong lol). Biggest risk I think is if the "printing" of the scale is off by a couple mm it could significantly impact the readings.

In any case if it is just clownfish no need to panic. Whether is is 1.020 or 1.025 they will be just fine. Just figure out which to trust going forward.

 

[Sasquatchv]

Mix some rodi water and table salt(pure NaCl) . I bet you $5 both will read the same/very close.
You need 35grams of salt to 1 liter of water.