Hydrometers

[DeepBlueZoas]

Hey Randy I was looking to find a reliable glass hydrometer to check the specific gravity in my tank. I bought one made by Marine Enterprises but it says that it is calibrated for 75 degrees F but my tank is never at that temperature and it did not come with a chart to compensate for temperature difference. I've heard some good reviews on tropic marine's hydrometer but was wanting to know if your had any advise as to which one you have seen to be consistently accurate. I have a 14gl nano and swings in SG can happen easily when doing water changes, and I have no idea what it is at now because my LFS has a refractormeter that is rusted so it can't be calibrated which said my level was at 1.028 and the hydrometer I bought says its at 1.022 so i dont know if I should lower it or raise it.

Thanks

 

[hkgar]

Here is a link to a chart to check your reading at tank temp to 75.

http://www.brewersfriend.com/hydrometer-temp/

 

[DeepBlueZoas]

Here is a link to a chart to check your reading at tank temp to 75.

http://www.brewersfriend.com/hydrometer-temp/

Thanks but I read in Randy's article on SG and hydrometers(link below) that all hydrometers are effected differently because they are all made with different materials and with different amounts of each material, and there are also many different temperatures that hydrometers were calibrated at mine is calibrated for 75 degrees F while tropic marine's I believe is calibrated at 77 degrees F



http://www.advancedaquarist.com/2002/1/chemistry

 

[disc1]

Thanks but I read in Randy's article on SG and hydrometers(link below) that all hydrometers are effected differently because they are all made with different materials and with different amounts of each material, and there are also many different temperatures that hydrometers were calibrated at mine is calibrated for 75 degrees F while tropic marine's I believe is calibrated at 77 degrees F



http://www.advancedaquarist.com/2002/1/chemistry

All the more reason to get a refractometer and be done with it.

 

[Dr. Reef]

i agree with David, i never had faith in hydrometers never will i rather use ATC refractometer and get is over with.

 

[hkgar]

i agree with David, i never had faith in hydrometers never will i rather use ATC refractometer and get is over with.

Absolutly right! One small air bubble that you don't see can effect the results. A little salt on the pivot point, calification that changes the arm weight.

 

[DeepBlueZoas]

Absolutly right! One small air bubble that you don't see can effect the results. A little salt on the pivot point, calification that changes the arm weight.

I am talking about a glass floating hydrometer and they are very accurate if used correctly and if a nice one is used. Which is what I was trying to find out here from Randy as to which one I should get I am not getting a refractometer I don't have enough money.

And I do not want to spend more money on a cheap refractometer than a nice hydrometer.

 

[disc1]

I am talking about a glass floating hydrometer and they are very accurate if used correctly and if a nice one is used. Which is what I was trying to find out here from Randy as to which one I should get I am not getting a refractometer I don't have enough money.

And I do not want to spend more money on a cheap refractometer than a nice hydrometer.

Randy hasn't been around for some time. We might see him some more in the summer.

You can use a floating glass hydrometer to good accuracy if you do it right. But you will have to deal with the conversion.

The density of the glass shouldn't change very much between 75F and 80F, so that term is negligible. The hydrometer is reading the specific gravity and making a conversion to tell you what it would be if the water were 68F where SG is standardized. That's the 1.026 number that we throw around so much. That is referenced at 68F, the actual density in our tanks isn't close to that. I mean if you weighed exactly one gram of water.

So now you're reading at say 80F, and that same conversion to 68F needs to be made. But your hydrometer scale is assuming the measurement was made at 75F when it does the conversion for you. Problem? No. All you gotta do is a little math to adjust that conversion and you can get there. I believe someone has already posted the table.

 

[DeepBlueZoas]

Randy hasn't been around for some time. We might see him some more in the summer.

You can use a floating glass hydrometer to good accuracy if you do it right. But you will have to deal with the conversion.

The density of the glass shouldn't change very much between 75F and 80F, so that term is negligible. The hydrometer is reading the specific gravity and making a conversion to tell you what it would be if the water were 68F where SG is standardized. That's the 1.026 number that we throw around so much. That is referenced at 68F, the actual density in our tanks isn't close to that. I mean if you weighed exactly one gram of water.

So now you're reading at say 80F, and that same conversion to 68F needs to be made. But your hydrometer scale is assuming the measurement was made at 75F when it does the conversion for you. Problem? No. All you gotta do is a little math to adjust that conversion and you can get there. I believe someone has already posted the table.

thank you yea I looked at the table that was given in the link and it shows no difference from 75F and 80F for the SG. So I believe it was just a poorly made hydrometer because i compared it to another and a refractometer and both read 0.004 or more higher than the one I bought made by Marine Enterprise. I am planning on just ordering the one made by tropic marin tomorrow.

 

[Ron Reefman]

i agree with David, i never had faith in hydrometers never will i rather use ATC refractometer and get is over with.

Absolutly right! One small air bubble that you don't see can effect the results. A little salt on the pivot point, calification that changes the arm weight.

Really guys?

Just for fun (and experience) I took 2 hydrometers that I 'calibrated' with a calibrated refractometer about 3 years ago. Both hydrometers were 'off' by different amounts. So I made labels and added them to the side of the hydrometer. Over the past 3 years I've recalibrated the refractometer 6-8 times and it's always been pretty close to accurate, but has needed adjustment. Every time I recalibrate the refractometer, I check it against the hydrometers... and guess what? They always have the EXACT same error rate they had 3 years ago. They may not be made very accurate, but if 'calibrated' they are extremely RELIABLE and almost unbreakable. IMHO hydrometers get a really bad rap here on RC. Try it yourself and see how one works for you. Sure you have to take care of it, just like you do with a refractometer. Just quit slamming them because they are cheap. You don't get air bubbles or salt on the pivot or calcium build up on the arm if you take care of it and pay attention to what you are doing. Don't be such equipment snobs. Do the test.

 

[bertoni]

I hear varying reviews about the swing arms. In theory, if they're kept clean, they should be okay. I used a conductivity meter, but I'm a bit obsessive about test equipment.