Hydrometer acuracy
 

I'm currantly in the process of setting up my tank and was wondering, how dependable is a Hydrometer? Does everyone use refractometers?

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a hydrometer isnt very dependable

when i had mine i had a reading of 1.026 which i though was good, but when i bought my water over to a LFS they tested at 1.021, so i ditch the hydrometer and got a refractometer

hope that helps
orbit

my hyrdrometer would read differently even if i tested the same sample twice. It was bad, my refractometer cost $60 from marine depot, and us always accurate!

My hydrometer would read dead on with my refractometer. I think even though they might be right you need something more accurate to check salinity. I purchased my refractometer off of ebay for about 40 bucks with shipping and it works perfect.

Yes, I've checked my salinity with my hydrometer on calibration solutions and it is dead on. Though, like you I will purchasing a refractometer very soon.

Sorry to piggyback, but is there any big difference between refractometers? More specifically on marinedepot the $50 one and the $69 one, seem about the same, anything else to know???

both my hydrometer and refractomter measure the same every time...and my hydro has hit the ground twice and lost its weight twice...still reads bang on...

as for refractometers i dont think there is much difference..but i dont know...i just bought the only one my LFS had..

My hydrometer is very accurate, tested against a refractometer. You have to keep them clean though and not let salt build up on the swing arm. I will probly buy a refractometer down the road though.

My deep six hydrometer is underreads .002. I checked with four different LFS refractometers within a four-week interval and all say my SG is 1.026 when my hydro says 1.024. My SG stayed constant for quite a while now and as of now I'm not worrying as much about my salinity as I did when I first began the tank.

I suppose deep six hydro are rather accurate but I state this clearly: WASH HYDROMETER WITH FRESHWATER FOR ABOUT TEN MINUTES SECONDS AFTER YOU USED IT IN SALTWATER

HTH

Thanks for the advice, I think I'll stick with my deep six hydro and upgrade to a refractometer down the road.

The swing arms are just not reliable. Anyone posting positive results are 1/1000. A floating hydrometer is not bad and a decent alternative to a refractometer. You're a newb, and Im sure there are plenty of things you want first, but I can gurantee you will never regret the decision to buy one early!!!!!!

[QUOTE][i]<a href=showthread.php?s=&postid=11495499#post11495499 target=_blank>Originally posted</a> by mfp1016 [/i]
[B]A floating hydrometer is not bad and a decent alternative to a refractometer.

What brand do you recomend?

I've had several hydrometers and found them to be inaccurate.

Hydrometers are not usually calibrated, so it is anyones guess...

I have one really cheap one that reads dead on, compared to my refractometer and a Deep-Six that is WAY off... The Deep-Six however is notoriously bad.

Important elements can be greatly effected by the salinity, so why risk it? Say your salt should read 1200ppt magnesium at s.g. 1.026 35ppt, but you are actually only at 32ppt (s.g. 1.024), now your mg is actually only 1097ppm. If you are actually at 28ppt (s.g. 1.021), now you only have 960ppm mg!

With a hydrometer, you just can't be confident. a refractometer is the best investment you can make in this hobby IMO.

i always rinsed my refractometer out with vinegar....

i use the refractometer. if you can afford the keep a reef, you can afford a refractometer. even if it means passing up that 45$ hammer coral you saw at the store.

I just got my refractometer today and noticed that my tank was 1.030 not 1.026!!! SO I took care of that

A good hydrometer should provide accurate and precise values if kept clean religiously. If deposits are allowed to build within the hydrometer, this will skew the results. But, as others have mentioned, if the hydrometer does not read correctly when new, it will NEVER read correctly, since it cannot be calibrated.

But, it would be a mistake to blindly state "refractometers are accurate" - the MUST be calibrated! An incorrectly calibrated refractometer is just as bad as a poorly manufactured hydrometer. And, calibration with just pure RO/DI water = 1.000 is not sufficient, since the prisms in refractometers are rarely perfectly accurate throughout the entire range of values we wish to measure. The best way to calibrate a hydrometer is with a calibration standard for refractive index. Randy has a great DIY recipe in his chemistry forum articles, if you have access to a graduated cylinder with ml or an accurate scale.

Also, keep in mind that refractometers must be kept extremely clean also, or they will be off. Since you are only measuring a very small volume of water (a few drops) with a refractometer, even the smallest grain of salt on the prism surface, or in the eye dropper you gather the sample with will have a BIG impact on the reading. The refractometer's prism surface AND the sampling tool must be thoroughly cleaned every time when you are finished using it.

mathias999u great advice - I would mostly agree.

Hehe, I invite constructive correction if I'm misunderstanding something. ;)

Thanks for all the responding! You guys have been very helpful.

The Hydrometer that came with my RSM looks like a flag waving in the wind. One day high one day low, I dont trust it at all.