Reef tank salinity weird readings.

[deepsynth]

Hey guys.

I’m confused big time. I am busy cycling my reef tank. I started with RO water and mixed my own salt to the instructions.

my initial reading with my hydrometer were on the cusp of 1.020 which I thought was cool.

attached please see the photo of the amount of evaporation. So from the top of the electrical tape to where it is now.

but the hydrometer reads the same reading or actually a bit less meaning it’s sitting deeper in the water .

the only difference I made was the tank was running initially at 23 Celsius but I turned up the temp to 31 to get the cycle going?

yes I know I need a refractometer I just can’t afford it right now.
Can anyone explain this to me.
Thanks

 

[wiktor]

Hey guys.

I’m confused big time. I am busy cycling my reef tank. I started with RO water and mixed my own salt to the instructions.

my initial reading with my hydrometer were on the cusp of 1.020 which I thought was cool.

attached please see the photo of the amount of evaporation. So from the top of the electrical tape to where it is now.

but the hydrometer reads the same reading or actually a bit less meaning it’s sitting deeper in the water .

the only difference I made was the tank was running initially at 23 Celsius but I turned up the temp to 31 to get the cycle going?

yes I know I need a refractometer I just can’t afford it right now.
Can anyone explain this to me.
Thanks

I wouldn’t honestly give much advice as we use different measuring apparatus however the water evaporation is normal, i lose roughly 8L of water to evaporation a week on a 4ft tank. My lights sit roughly 8-10 inches above water level i think Some have it much lower to water btw. My salinity i aim for 1.025-1.026, before water changes weekly it usually rises to 1.028 by the time i change out 10-15% of water.

 

[TheBear78]

What is the actual reading now? "Sitting lower" doesn't tell us much!
When you initially measured 1.020 was this in a bucket, in the tank before pumps had circulated the water or after a few hours to fully stir the mix?

 

[Sasquatchv]

Hey guys.

I’m confused big time. I am busy cycling my reef tank. I started with RO water and mixed my own salt to the instructions.

my initial reading with my hydrometer were on the cusp of 1.020 which I thought was cool.

attached please see the photo of the amount of evaporation. So from the top of the electrical tape to where it is now.

but the hydrometer reads the same reading or actually a bit less meaning it’s sitting deeper in the water .

the only difference I made was the tank was running initially at 23 Celsius but I turned up the temp to 31 to get the cycle going?

yes I know I need a refractometer I just can’t afford it right now.
Can anyone explain this to me.
Thanks

You don't need refractometer. Hydrometer is as accurate, just a bit cumbersome, BUT once calibrated stays calibrated untill physically broken.
As mentioned above, salt need some time to fully dissolve.
Hydrometer reading will change with temperature, as water expands when heated.
Your hydrometer should have calibrated temperature printed on the scales. It reads true at that temperature. There are calculators online to adjust reading for different temperatures.

To get semi insta cycle without bac in bottle expense pick up piece o live rock from your local fish shop sump. Fist sized rock cycled my 33galons in 10 days(got it free with salt purchase).

 

[deepsynth]

What is the actual reading now? "Sitting lower" doesn't tell us much!
When you initially measured 1.020 was this in a bucket, in the tank before pumps had circulated the water or after a few hours to fully stir the mix?

Measurements were done in the tank after a day of running. I turn everything off and then measure 30 min after that.
When I saw sitting lower it’s going from 1.020 to 1.019 or 1.018

 

[deepsynth]

You don't need refractometer. Hydrometer is as accurate, just a bit cumbersome, BUT once calibrated stays calibrated untill physically broken.
As mentioned above, salt need some time to fully dissolve.
Hydrometer reading will change with temperature, as water expands when heated.
Your hydrometer should have calibrated temperature printed on the scales. It reads true at that temperature. There are calculators online to adjust reading for different temperatures.

To get semi insta cycle without bac in bottle expense pick up piece o live rock from your local fish shop sump. Fist sized rock cycled my 33galons in 10 days(got it free with salt purchase).

This is all news to me. Calibration of a hydrometer. Temp readings.
I thought you put it in the water and where it floats is the reading

 

[Freenow54]

the salt does not evaporate therefore the reading remains the same. you may get lower readings due to salt " creep ". When adding water to top up hopefully rodi do not add salt

 

[Uncle99]

Just keep the salinity and temp stable at whatever your future inhabitants like. Stability from the start, advances your system faster, with less trouble.

 

[Freenow54]

Just checked on amazon REFRACTOMETER $25

 

[Mr. Mojo Rising]

This is all news to me. Calibration of a hydrometer. Temp readings.
I thought you put it in the water and where it floats is the reading

that thing that floats in the water is not reliable at all, you should put it aside and get a good quality instrument before doing anything more.

 

[EeyoreIsMySpiritAnimal]

This is all news to me. Calibration of a hydrometer. Temp readings.
I thought you put it in the water and where it floats is the reading

No. Sealed glass Hydrometers are calibrated to either 60 F (15.6 C) or 77 F (25 C).
Salinity of 1.020 at 23C is about 1.0189 at 31C. So with evap, salinity of 1.020 at 31C seems reasonable.

*Edit: the above values are for a hydrometer calibrated to 77F

 

[EeyoreIsMySpiritAnimal]

that thing that floats in the water is not reliable at all, you should put it aside and get a good quality instrument before doing anything more.

This is completely incorrect

 

[Sasquatchv]

Just checked on amazon REFRACTOMETER $25

Cheap ones are usually scaled for salt only, not seawater, thus scaled from SG 1.000 to 1.060. good luck reading 0.001 difference on them with 100% certainty. I have one of those, and bought hydrometer to really know where my salinity is.

This is all news to me. Calibration of a hydrometer. Temp readings.
I thought you put it in the water and where it floats is the reading

I meant hydrometer calibrated at factory will never need reacalibration.
All you have to do is adjust reading to your tank/fresh mixed water temperature to get true salinity.
Using this calculator : https://www.vinolab.hr/calculator/hydrometer-temperature-correction-en31
or use formulas provided in a spreadsheet for offline use.

 

[deepsynth]

Just checked on amazon REFRACTOMETER $25

I wish I lived in the states. I come from South Africa, so on top of a hectic exchange rate our government usually taxes imports between 40-80%

 

[deepsynth]

No. Sealed glass Hydrometers are calibrated to either 60 F (15.6 C) or 77 F (25 C).
Salinity of 1.020 at 23C is about 1.0189 at 31C. So with evap, salinity of 1.020 at 31C seems reasonable.

*Edit: the above values are for a hydrometer calibrated to 77F

Oh ok I understand. So basically the hydrometer read a result at a certain temp. That’s really interesting, before I replied to you I did see that there is a chart for differences in temp.
So do you believe that it’s accurate or should I invest in a refractometer

 

[deepsynth]

Cheap ones are usually scaled for salt only, not seawater, thus scaled from SG 1.000 to 1.060. good luck reading 0.001 difference on them with 100% certainty. I have one of those, and bought hydrometer to really know where my salinity is.
I meant hydrometer calibrated at factory will never need reacalibration.
All you have to do is adjust reading to your tank/fresh mixed water temperature to get true salinity.
Using this calculator : https://www.vinolab.hr/calculator/hydrometer-temperature-correction-en31
or use formulas provided in a spreadsheet for offline use.

Thank you this is perfect. Pretty much exactly what I needed.

 

[EeyoreIsMySpiritAnimal]

Oh ok I understand. So basically the hydrometer read a result at a certain temp. That’s really interesting, before I replied to you I did see that there is a chart for differences in temp.
So do you believe that it’s accurate or should I invest in a refractometer

I believe it's not going to drift... I can't comment on the overall accuracy since it *could* have been calibrated incorrectly at the factory, but once you account for temp, it will give you consistent readings.
I won't tell you not to buy a refractometer, but I don't think it's necessary.