Hydrometer question

[Lovesfish]

Can a hydrometer be broken? I have one and the readings its giving just don't seem accuate at all. thanks in advanced

 

[steelhealr]

The main problem is bubbles that adhere to the swing arm. They are very inaccurate. If you are serious about keeping a marine system, I'd invest in a refractometer. Much easier..more clean..more fun to use. ...and drier. SH

 

[blout]

i agree with SH i had a hydrometer which always said that salinity was 1.021 but i broke that and bought refractometer and straight away the salinity read alot heigher (1.024) which is not what i liked to see, so def worth the extra cash

 

[Chac]

I would never rely on a Hydrometer TBH - I got a refractometer the day I bought my 1st load of live rock

 

[steelhealr]

I've found them to be off by at least .003-4....agree above. That is a big difference if you are keeping some corals. SH

 

[Navarre]

I would not be without my Refractomoeter now. Its one of the best buys i made for my tank.

 

[Lovesfish]

is the hydrometer off this link anyway good? I thought I would ask before I spend the money on one because I want a good one that will acutally work. thankshydrometer link

 

[maestro]

The problem with refractometres though is that they ones used are all meant to read brine -saltwater, not actual seawater so arent as accurate as people think

 

[superman]

The problem with refractometres though is that they ones used are all meant to read brine -saltwater, not actual seawater so arent as accurate as people think

Maybe so, but consistancy of an acceptable salinity is often much more important than the exact salinity level itself. The main reason that I chose to get a refractometer is the fact that hydrometers are very iffy when it comes to differing temperatures between two bodies of water that you are trying to make the same salinity (example: Your tank and your saltwater mixing bucket)

 

[maestro]

a lab grade hydrometer would be much more accurate than a refractometer, I just think its wrong that if people have 2 readings they automatically assume that the refractometer is the correct measurement even though the ones available for hobbysist arent designed to read seawater

 

[Navarre]

Weather they are designed for marine water or not there is no argument that they are consistantly more stable. I would rather us a refractometer thats consistantly .02 out than a hydrometer that can read 1.022 on one day and 1.024 on another for the same body of water.

 

[Ed4567]

Oh dear specific gravity
Firstly, in short it is absolutly meaningless to compare the specfic gravity shown by two different instruments unless you know the temperature of water they were designed to test, and what they are comparing it to (specific gravity is a bit like a ratio).

Secondly, many people think the accuracy of an instrument is dependant on the way it operates, for the most part it's not. The accuracy depends on how well manufactured and designed it is.

Thirdly I've read this quote on another forum and I think it's quite appropriate:
"buy fish from your LFS, lights from an electrical supplier....and hydrometers from a lab supplier. Don't confuse them."

These hydrometers were recommended, and they certainly look good:
http/www.brannan.co.uk/products/hyd_specgrav.html

Ed

 

[steelhealr]

Hi...those types are fine too. I wouldn't get too worried about the refractometers. Thousands of us are using them and have thriving tanks. If you are REALLY interested, buy one and then measure ocean water and see what you come up with. I think what is most important is to keep it calibrated with RO, and, like most other 'experiments', if your livestock are thriving and you use the same refractometer and same procedure, consistency is more important.

Comparing the differences between 2 instruments IS important if you are trying to determine the 'DIFFERENCES' between the two. Considering that the refractometers are built to adjust for temp, you don't need to worry about it if you let the water sit on the viewing area for 30 secs. Also...., if you are comparing the two against your tank temp, temp is unimportant in that it is a stable variable.

I think most would agree that an plastic hydrometer is a very inaccurate piece of equipment. Finally, JMO, although the glass float hydrometers maybe very accurate, I for one would rather hold an instrument up to the light and look thru an eyepiece than strain my eyes and stair at a water line on a bobbing glass tube, or, drip SW all over the floor with a hydrometer. Again, JMO. SH

BTW..these are on sale now. http/www.drsfostersmith.com/product/prod...=1&N=2004&Nty=1

 

[Ed4567]

Also...., if you are comparing the two against your tank temp, temp is unimportant in that it is a stable variable.

Sadly not this simple. If two hydrometers are calibrated for water of different temperatures, then they will give different results even when testing the same water. More worrying (if you are really concerned about accuracy) most hydrometers won't even tell you what this temperature might be.

Anyway I agree a properly calibrated refractometer is suitable and certainly has advantages (small amount of water needed etc.), but isn't the be all and end all of salinity measurement.

 

[Lovesfish]

I mixed a batch of saltwater that I knew the concentration from based on the box and found the hydrometer to be off by the same amount evey time. so till I get more money I can just add the difference to my readings to get what the salinity. thanks for the info about the error it helped greatly . I will have to take some pictures of my tank and post them up here soon.