A Review On Accuracy Of Salinity Measurement Appar

[CalciumReef]

A Review On Accuracy Of Salinity Measurement Apparatus

In our marine hobby, one of the most important issues is providing a suitable environment for our aquarium inhabitants. Water's salinity level is one of the important properties in captive marine environment. Water that is either too saline or not saline enough, which can be stressful or lethal to tank inhabitants.

There are a few salinity measurement apparatus available in the market. They include specific gravity (via hydrometers), refractive index (via Refractometer), conductivity (via electronic meters). If the device used is properly calibrated, maintained and used, derived values will be ideal but there are always cases of wrong readings due to human error or equipment failure.

In terms of price from cheapest to most expensive, the rankings are hydrometers, followed by Refractometer and lastly electronic meters.

More information on the above salinity measurement apparatus:

Floating Hydrometer

Swing Arm Hydrometer

Refractometer

Conductivity Salanity Measurement Apparatus

DigiLab Handheld Salinity Tester

Americian Marine Pinpoint Salinity Monitor

A more detailed review in reefkeeping online magazine:

Review

**There has been saying of conductivity meters being inaccurate due to stray voltage, which could be present in water. Collecting the water sample in advance and testing it remotely could solve this issue.

[CalciumReef]

Below are factual readings taken from the same sample of water(35ppt) using different available salinity measurement apparatus’s that I managed to get hold of. Anyone with other apparatus is welcomed to post their measurements as well.

Swing Arm Hydrometer

[CalciumReef]

A closer look at the readings, showing 28ppt when standard is 35ppt which relates to 1.026

[CalciumReef]

JBJ DIGI-LAB salinity Handheld tester

A look at what's inside the box

[CalciumReef]

What makes the JBJ DIGI-LAB salinity Handheld tester accurate enough

[CalciumReef]

Here's the reading, just nice at 35ppt

[CalciumReef]

Refractometer

A look at what's inside the box

[CalciumReef]

Refractomer also gives a reading at 35ppt

[CalciumReef]

Conclusion:

In my opinion, conductivity salinity measuring apparatus are easy to use as compared to hydrometers. However, hydrometers somehow tend to show deviated readings which could be quite detrimental to marine inhabitants.

Conductivity salinity measurement apparatus such as the DIGI-LAB and Americian Pinpoint Salinity monitor are on par with the refractometer and does not require frequent calibration and yet more convenient to use than a refractometer.

Regarding hydrometers showing deviated readings, there is a way to solve this issue. Borrow from someone who owns a Refractometer or salinity tester or monitor to tally the readings against each other. From there you will know the deviation value to be factored into the final reading.

Happy reefing

[Gouldian]

Good job bro!

I have done the same test previously and have the same conclusion.

In my test, I have also tried the Sera Glass Floating Hydrometer, found that it closer to the actual as compared to Swing Arms.

Thanks for sharing.

[Jameshong]

I think the accurancy measurement very related to cost . The more accurate the equipment/tool can measure, the more expensive it is lor !

A sign of high cost hobby again

Anyway, it is a good review!

Thank Bro.

[Jameshong]

JBJ DIGI-LAB salinity Handheld tester

A look at what's inside the box

Hi CalciumReef,

It is more simple and easy to use this JBJ DIGI-LAB salinity Handheld tester !

Care to share, how much do u bought this ?

[May&Bruce]

Guys, the following might also help to explain things.

Hydrometers are normally calibrated at a temperature much lower than some of us keep our reefs. The article below says that most are cablirated at 60 F = 15.6 C. This sounds a bit low to me - I think some are caliobrated at 25 C. In any case, the point is that at if your tank is at a higher temp than the temp that your hydrometer is calibrated at, then you need to adjust the reading based upon the tables below.

Best device would seem to be a properly calibrated temperature compensated conductivity meter...but the price lah!

1.3.6 Specific Gravity

Short form: Specific Gravity is temperature dependant. See the next table for a quick lookup of the recommended hydrometer readings. They are based upon our recommended S.G. of 1.025 at 60 degrees F.

Degrees F. Hydrometer reading.

50 1.0255

55 1.0252

60 1.0250

65 1.0246

70 1.0240

75 1.0233

80 1.0226

85 1.0218 (rather hot for most tanks)

90 1.0210 (very hot for most tanks)

In more detail: 1.025 recommended for reef tanks. Note that virtually all hydrometers are calibrated for measurements at a temperature of 60 F. Included below is a short table of temperature adjustments. Add the value shown to your hydrometer reading to get an accurate reading.

Degrees F. Correction

50 -0.0005

55 -0.0002

60 0.0000

65 0.0004

70 0.0010

75 0.0017

80 0.0024

85 0.0032

90 0.0040

For example: If the hydrometer reads 1.0235 at 80F, the actual Specific Gravity is 1.0235 + 0.0024 = 1.0259

Note: If your tank is between 75F and 80F, this means you should try and keep your Specific Gravity around 1.0230 to 1.0235.

For all practical purposes, the scale is linear between data points, so you can simply extrapolate between table entries. For instance, 78F is 3/5 the distance between 75F and 80F; the difference in corrections is 0.0024-0.0017 = 0.0007. 3/5th of 0.0007 is 0.0004. Add the offset 0.0004 to the base value for 75F of 0.0017 and you get a correction value for 78F of 0.0021.

It is fairly common in literature to see references to salinity in terms of Parts Per Thousand (PPT). For salinities in the range we are interested in, the conversion formulas are:

Salinity = 1.1 + 1300 * (Temperature corrected Specific Gravity - 0.999)

Temperature corrected Specific Gravity = ((Salinity - 1.1) / 1300) + 0.999;

Here is a short table of some common values:

Salinity Specific Gravity

20 PPT 1.0135

25 PPT 1.0174

30 PPT 1.0212

35 PPT 1.0251 * Typical Ocean Value *

40 PPT 1.0289

[gunzo]

thanks very much for this review.. went to buy a refracto just to be sure.. I've been running my tank at 1.032 for a long while!!

no wonder i have so much problems with fish adapting!

i lowered the salinity (good time to change water!) to 1.026..

to think i was on 1.023 with a hydrometer!.. not even close.. mine was 'calibrated' for 25 degrees celcius somemore...

next drop salinity to 1.023

[Rex Ng]

good review

[Angel]

Hi CalciumReef,

It is more simple and easy to use this JBJ DIGI-LAB salinity Handheld tester !

Care to share, how much do u bought this ?

Bought an OEMed version of the JBJ having the same features for S$139 only.

[CalciumReef]

Bought an OEMed version of the JBJ having the same features for S$139 only.

Does the set come with warranty?What i understand is that JBJ brand comes with a 6mth warranty.

[Angel]

Does the set come with warranty?What i understand is that JBJ brand comes with a 6mth warranty.

Yes. It comes with a 6 month warranty under normal usage.

[cityofangels]

Good review. I guess it's about time I invested in a good Refractometer.

[May&Bruce]

Coralife Deep 6 floating arm hydrometer is reasonably accurate though:

This durable hydrometer takes true water

samples 6 inches below the water’s surface

- without your hands coming in contact

with the water, preventing contamination.

Holding the top of the hydrometer with

your thumb and index finger, simply

submerge the lower portion of the

hydrometer to obtain the sample. The

hydrometer does not require temperature

corrections and gives direct readings in

ppt and specific gravity. In addition, each

hydrometer has been pre-calibrated and

tested for guaranteed accuracy. Range: 16

to 40% ppt (1.010 to 1.030 sg). Accuracy:

±0.001 specific gravity

.....according to the sales literature.

Assuming that your tank is around 1.023 - 1.025, I would think that the more critical issue (as with most parameters) is not to have large fluctuations in SG, in which case such a hydrometer should be sufficient for monitoring fluctuations.

..... having said all of that, I will probably get a refractometer too, within the next 6 months

[loster]

good review.

i used to use hydrometer in the beginning of my reeefing. and i didn't know that my tank runs at 1.028-1.029 when i measure it with my new purchase refractometer

[jervismun]

Great review! That's it, I'm gonna get a Digilab tomorrow.

[jervismun]

Bought it! Nice... now I can check my water daily without getting my hands wet or stressing the LS too much by submerging my old Coralife swing-arm.

[JeffL]

sorry for digging up this rather old thread but I guess this is something relevant to what I am looking for.

Anyone using digital Salinity tester? The one from JBJ has been discontinued and I am looking for a handheld tester which allows me to measure my salinity levels easily.

The Pinpoint tester is out of my budget....

Found this online in Singapore. Not sure if anyone is using and can provide some feedback but it seems like the choices are very limited.

[Jameshong]

Interested to know too.