Salinity meters/hydrometers
 

Anyone else have trouble with salinity meters? I have 3, all read differently, I bought a glass hydrometer and checked it on RO water, it read 1.003 .I used the three different hydrometers on my tank water and got readings of 32ppt or 1.0235, 37ppt or 1.0275, and 36ppt or 1.0265. My glass hydrometer measured the tank water at 1.029 or 39ppt. That's a rather large range of readings and leaves open some potential for trouble. I didn't really want to have to spend the bucks on a refractometer but I am thinking it's the accurate way to go.

Do I have other reasonable options?

Douglas

And before anyone asks yes they were all soaked in RO water for 24 hours

I just went to a refractometer and am amazed well worth the price.

Refractometer - THE ONLY way to go! Well worth the investment and you may be able to find one used for half the price!

Refractometer hands down!! You can get them fairly inexpensive if you look around.... like $40. $40 to keep hundreds or thousands of $$$ in live stock alive is worth it to me.

BCOrchidGuy....... I am a cheap SOB :) But I think my refractometer was well worth the cost. My hydrometer was showing 1.023 and my refractometer showed it was really 1.031. Wow......

Well, considering the cost of the IO one I have, the Coralife one and the Red Sea, plus the glass one I could have bought a refractometer. I guess that's next on the shopping list.

Thanks for the replies folks

Certainly refractometers are easiest and fastest but a clean, calibrated and appropriate hydrometer is more accruate. To be clear I mean a long glass cylinder hydrometer, not the plastic swing arm type found in Capt. Crunch cereal boxes.

Are you reading the glass hydrometer correctly? Make sure you are reading at the lowest level of the Meniscus.
http://en.wikipedia.org/wiki/Meniscus

What model of hydromter are you using? It will be somewhere on the paper within.

Yes reading from the bottom of the meniscus, I think it is a coralife but the paper insert must have moved because it was floating higher than it should have been. Not a big deal I know you need to compensate on them but the plastic ones are all over the place with the readings. Oh and one air bubble can screw up the arm on the plastic ones as well, make it read wayyyy higher.

Douglas

If you suspect the paper has moved in any hydrometer, chuck it out. Useless.

Any good glass hydrometer will have a green or red mark on the inside of the glass that matches same mark on the paper. If they don't line up then the paper has moved. Chuck it.

Chucked !!! with extreme prejudice

Have a Refractometer myself but do laugh a bit as we (myself included) go on how they're so much better than a swing arm hydrometer.

Been ages since verified mine against ro water and never have actually made a test solution for the range in which I use mine. Really without frequent verification there are no better than a swing arm type.

With swingarm & glass hydrometers people often don't realize or forget that these are calibrated at a set temperature and if the water you are measuring is significantly off that temperature, it will affect the reading. Most of the newer refractometers have automatic temperature compensation so provided you wait a few moments for the liquid to reach temperature parity with the refracto, you're good to go.

I just measured my tank water with 4 different components:;

Glass Hydro with thermometer: 1.024+ @ 74 Fahrenheit (there's a mark at 78 F so I assume that's the manufacturer's calibration temperature)
Refractometer: 1.024+ (auto temp compensation)
Instant Ocean swing arm: 1.0234 @ ? Fahrenheit, presumably same as glass hydro
Coralife Deep Six swing arm: 1.0216 @ ? Fahrenheit - same story as IO swing arm

Note the extra decimal place for the cheapo swing arm jobbies. That's because the scale on both of these is fairly large making it easier to read off to that level of accuracy. Both the glass hydrometer and refracto scales are much tighter and for me this makes it almost impossible to read anything beyond that 3rd decimal. So one could argue that the swing arm hydros offer an advantage in this regard, provided they are accurate to begin with and one has the temperature compensation chart handy.

I kind of like the floating glass hydrometer. It's a tried and true technology. Different versions of these have been used for decades to measure specific gravity of battery acid, anti freeze in your radiator, sugar content for potential alcohol of that home made wine.... Same goes for refractos, one for almost every flavour.

At $50.00 each and as delicate a rose, this is the glass hydrometer to use if you want to measure your SG/Density to an accuracy of 0.0005

Fisherbrand* ASTM* Specific Gravity Hydrometers for Liquids Heavier than Water > ASTM: 111H; Range: 1.000 to 1.050

Hydrometer, Specific Gravity; Fisherbrand ASTM; For Liquids Heavier than Water; ASTM: 111H;Range: 1.000 to 1.050; Division: 0.0005; 330mm L; Made from polycarbonate for glass-like clarity; Use with11-582-1 Cylinder

God I love lab gear.



http://www.fishersci.com/wps/portal/...e&fromSearch=Y

I have a refractometer. I use it to calibrate my Sea Test Hydrometer. I have found that my hydrometer is out by .03! So, when I use it on a day to day basis i just add .03 to it and it's corrected. The real key is having the consistient salinity. That includes same salinity in the tank and water change salinity.

I re-test my hydrometer every time I do a water change just to make sure it holds.

Remember resolution is different than accuracy.

+1 on the consistency. I usually double/triple check to ensure my water change salinity is as close as possible to the display water.

Here are some photos of my measurements with the different 'instruments'.

IO Swing Arm 1.0234

http://hlj1yw.blu.livefilestore.com/...OSwingArmB.jpg

Coralife Swing Arm 1.0126

http://hlj1yw.blu.livefilestore.com/...eSwingArmB.jpg

Made In Taiwan Floating Glass 1.024+ (same result as refracto)

http://hlj1yw.blu.livefilestore.com/...lassHydroB.jpg

what about pinpoint salinity meters?

1.0126?, good thing you cross check with the others:biggrin:

He, he, I haven't used the swing arms for quite some time. I've been using the refracto and floating glass hydro for quite a while now. Just thought I'd bring the swing arms out and give everyone a picture... worth a thousand words I'm told.

That's how a calibrated glass hydrometer works. With a couple of known solutions measure the standard deviation and then apply that deviation to the observed reading.

So once you know your hydrometer consistently reads +.03, add that to the observed result for an accurate measurement.

Of course by measuring anything you are changing it so you can never have a "TRUE" 100% no questions asked result. :lol:

you know you can't add another decimal there. the swing arm measures 1.023. If you wanted to extrapulate I would say your arrow looks more like 1.0236. at any rate your accuracy is only as good as your smallest measured value. so your swing arm has a accuracy of +/- 0.001

as with anything some are better than others, I got a refractometer from a fiah store and it reads 3 decimal places like the ones here, I picked one up some where else, paid a bit more money for it and it reads 4 decimal places.

One note about floating glass type, the reading changes with changes in barometric pressure, and 3 different people will get 3 different readings off them due to the water meniscus and the angle they look at it. Oh and the break easy :sad:. I use them for making wine only, my tank gets the refractometer (well the wine might also as soon as a find a decient one that is cheep.:mrgreen:)

Steve

It's kinda gettin silly.

First and formost, if you test the bucket of replacemnt water and the tank water with the same piece of equipment (float, swing arm, refractomerer, picnometer what ever..) and the slainity is close or the same great!. If you tank/livestock is doing well at .024 great that means every thing is aclimated to that salinity. If its .019 and every thing is thriving so be it. It simply must be consisitent or a slow change to allow everything to adapt.

If you are having a problem, then worst case senairo take a tank water sample to a local store that has a refracometere and have them test it. Then test with your apparatus. Bob's your uncle. make the changes you need to, and re-test your corrections (for aparatus of choice) on a regular basis.

Easy.

That is regarless of what school of thought you subscribe to in regards to salinity level.

I'll just be buying a refractometer to start off with, to alleviate any issues. I mean, for only 40 bucks, why not?

exactly, it always amazes me that people have no problem spending 500 on rock, and thousands on coral but cheep out on test equipment.

having the most accurate method of measuring your salinity isn't getting silly either, as a lot of problem can come from salinity and if you don't know if your device is off or not how can you find the problem? Just ask Aquattro what happens when you trust old swing arms to much :mrgreen:

Steve

imo, take the hydrometers and throw them in the trash. they are horriably calibrated

switching to a refractometer is probably one of the best things you can do for a reef tank