Testing salinity

[ianmphua]

Hi, i’ve just found out that refractometers have to be calibrated often using some sort of calibration fluid? This seemed like quite a hassle to me so i was wondering how often this calibration process would have to take place, and is the calibration fluid widely available for purchase once the existing bottle has run out? Or can tap water be used to calibrate the refractometer? Thanks!

 

 

Sent from Singapore Reef Club mobile app

[CharlieBrown]

I just pickup this hobby again after 20yrs. Many new tricks and toys on the market. Regarding salinity measurement, I bought a simple swingarm type and a even cheaper floating hydrometer which was what I use in the 90s. Fortunately both readings are pretty close. 

Also bought online a refractometer as well a cheapo digital one out of curiosity (never use these during my time). You need the calibration fluid. Common in the shops and online is the Salifert brand. 

[Indeco]

Hi, i’ve just found out that refractometers have to be calibrated often using some sort of calibration fluid? This seemed like quite a hassle to me so i was wondering how often this calibration process would have to take place, and is the calibration fluid widely available for purchase once the existing bottle has run out? Or can tap water be used to calibrate the refractometer? Thanks!
 
 
Sent from Singapore Reef Club mobile app

The calibration fluid is quite easy to get nowdays as more LFS is bring in.

The Standard 35ppt solution.

I used to calibrate my refractormeter using the solution and tap water to check the range. Tap water should measure 0 ppt.

It will be better to use both instead of either one.

For me refractormeter is quite troublesome to use and accuracy run off when u knock and hit it.

But after getting Hanna salinity checker, life is so much easy when come to checking salinity. If u don't mind the price tag I strongly recommend u get one.

[equiox]

Izzit very accurate? 

[CharlieBrown]

I have also switched to a Hanna HI98319. Its much easier and convenient to use. 

The principle is indirect measurement but because it is so consistent, coupled with intermittent calibration (I do it about every 2 months), the accuracy is very acceptable for hobbyist like us. Definitely more reliable than the swingarm and the common optical refractometers (very wide quality variations and calibration always run-off for some reason, so even though theoretically these are accurate, mfg quality makes them very unreliable IMO).

If you want highest accuracy (and quality), then the Hanna HI96822 (optical digital refractometer) is a great choice (but IMO not required)

On a related note, besides salinity, I find that accurate measurement and stability of alkalinity is also critical as corals consume them quite fast if you have many of them in a tank. A Hanna alkalinity checker is also great. The rest like NO3 and PO4, you can use Nyos kits which are decently good (of course you can also get digital checkers like Hanna as well if cost is not an issue).

For me, I am a low tech hobbyist and able to monitor the salinity and alkalinity are crucial for success in low tech tanks.