Hydrometers scales.

[atoll]

Seems the best and one of the most accurate ways (and cheapest to measure salinity in our tanks (and without even the need to calibrate them) is with the good old tried and trusted hydrometer. You know the one you either float in the tank or in a sample of water.

Now, the scales on most of these hydrometer have not changed in all the years I have been in the hobby, around 37 years now.

They are calibrated to read at a temperature of 25c. On the scale they have a green area that they recommend you keep your salinity at, usually from 1.018 to 1.026.
My question is why? We have long since ascertained that the best salinity for a reef tank is 1.026 which equates to 35ppm so at the top end of the scale (actually at the bottom reading on the hydrometer) surely what would be better is a line in the middle of the green area showing 1.026? Also perhaps the hydrometer should be set to read at 26c not 25. The salinity of1.026 reading being in the presipes of undesirable range with the current hobby hydrometers I have found.

Perhaps I am being over picky above but our hobby has moved on since hydrometers became available to us.

BTW I have a TMC floating hydrometer. 2 refractometers, one a read sea one and also a digital salinity (conductivity measuring converted to ppm) I threw away a swinging needle hydrometer years ago, most awful inaccurate things I have come across.

 

[CNDReef]

Id assume because it’s used in fish only systems that don’t need the salinity that high.
So instead of 2 different ones the just give you a range.

 

[RobB'z Reef]

Seems the best and one of the most accurate ways (and cheapest to measure salinity in our tanks (and without even the need to calibrate them) is with the good old tried and trusted hydrometer. You know the one you either float in the tank or in a sample of water.

Now, the scales on most of these hydrometer have not changed in all the years I have been in the hobby, around 37 years now.

They are calibrated to read at a temperature of 25c. On the scale they have a green area that they recommend you keep your salinity at, usually from 1.018 to 1.026.
My question is why? We have long since ascertained that the best salinity for a reef tank is 1.026 which equates to 35ppm so at the top end of the scale (actually at the bottom reading on the hydrometer) surely what would be better is a line in the middle of the green area showing 1.026? Also perhaps the hydrometer should be set to read at 26c not 25. The salinity of1.026 reading being in the presipes of undesirable range with the current hobby hydrometers I have found.

Perhaps I am being over picky above but our hobby has moved on since hydrometers became available to us.

BTW I have a TMC floating hydrometer. 2 refractometers, one a read sea one and also a digital salinity (conductivity measuring converted to ppm) I threw away a swinging needle hydrometer years ago, most awful inaccurate things I have come across.

dont really care about the scale part but these are a must have in any reefers tool box IMO. There are a lot of fancy pants ways these days to measure salt but they all drift over time and having a glass hydrometer on hand to use as a baseline for calibrating and auditing your other devices is a life saver in my experience.

 

[Dennis Cartier]

Let me do a PSA here. If you order any hydrometers in from EU countries, like Germany, you need to be aware that they will most likely measure density (g/ml), not specific gravity. TM makes both versions.

The 3 on the right measure density, the 1 on the left SG.

Mistaking one for the other will lead to some unhappy tank inhabitants ....

 

[Dennis Cartier]

Also I should add, the TM hydrometer measuring in SG has 1.026 positioned directly in the center of the shaded area, which is what @atoll was wanting (I believe). So perhaps time for some new hydrometers atoll?

 

[Randy Holmes-Farley]

Mine from 15 years ago had the "blue" zone lower too:

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated!

This month, Randy explains and reviews specific gravity.

reefs.com

Figure 4. A Tropic Marin hydrometer showing the meniscus rising to about 1.0260, but the actual reading is about 1.0265.

 

[atoll]

Also I should add, the TM hydrometer measuring in SG has 1.026 positioned directly in the center of the shaded area, which is what @atoll was wanting (I believe). So perhaps time for some new hydrometers atoll?

My 1.026 isnt in the middle its at the bottom of the green area they recommend you have your SG in. I have looked online at a few inc Aqua medic and Tropic marine both expensive ones and they are the same.

 

[atoll]

Mine from 15 years ago had the "blue" zone lower too:

Chemistry and the Aquarium: Specific Gravity: Oh How Complicated!

This month, Randy explains and reviews specific gravity.

reefs.com

Figure 4. A Tropic Marin hydrometer showing the meniscus rising to about 1.0260, but the actual reading is about 1.0265.

Outside the blue scale which I believe is what they suggest you keep your SG within

 

[Dennis Cartier]

My 1.026 isnt in the middle its at the bottom of the green area they recommend you have your SG in. I have looked online at a few inc Aqua medic and Tropic marine both expensive ones and they are the same.

Are you looking at the Tropic Marin High Precision Hydrometer measuring in specific gravity? Because all the high precision ones I have, for both Tropic Marin and Aqua Medic, have the measurement for 1.026 (or equivalent 1.023 g/ml) right in the center of the shaded area. See photo above.

@25C, 1.026 sg = 1.023 g/ml

@25C, 35 ppt = 1.0264 sg = 1.0233 g/ml

 

[atoll]

Are you looking at the Tropic Marin High Precision Hydrometer measuring in specific gravity? Because all the high precision ones I have, for both Tropic Marin and Aqua Medic, have the measurement for 1.026 (or equivalent 1.023 g/ml) right in the center of the shaded area. See photo above.

@25C, 1.026 sg = 1.023 g/ml

@25C, 35 ppt = 1.0264 sg = 1.0233 g/ml

Yeah the hydrometers in your photo show 1.023 in the middle of the shaded area. I was taking that as SG not g/ml. I thought SG was more appropriate for recording hence why I was fooled.

 

[taricha]

I threw away a swinging needle hydrometer years ago, most awful inaccurate things I have come across.

I love my Instant Ocean swing-arm hydrometer. The numbers they put on it are nowhere close, but after marking on the scale with my own S.G. standards, I find it to be really repeatable.
But I think I'm in the minority opinion on that one.

 

[atoll]

Now just need to keep it around there.

 

[polywise]

my hydrometer used weekly (bought early 1990's) best tool for happy reefing..