Testing Salinity

[dsn112]

Hey all, I have a few questions about testing salinity. I use a Coralife Hydrometer, and my tank has been running for almost a week.

I have tested numerous times and have been all over the place.

Today I tested and it was different in 3 different locations in the tank.

The deepest reading was 1.021

The Shallow reading was very low

and the other random spot was to left the gauge all the way up, which would be high.

Is my hydrometer broken, or is my tank out of whack?

Also a note, when I run freshwater through it the gauge points all the way up too.

Dave

[spanglish]

Well, the first thing you need to do is throw away the
hydrometer.

:D

No, really.

I know there are extreme opinions that fly around on some
of these forums, but EVERYONE whose opinions I have come
to value agrees that hydrometers (no matter what brand,
but especially "swing arm" types) are trash.

Spend the money and get a refractometer.

It is a necessity.;)

[marduc]

yes swing arm hydrometers are notoriously inaccurate. Until you get that refractometer though, make sure it is thoroughly washed out and flushed after each use with fresh water to minimize salt deposits. Also make sure to completely fill it with water, then tap/shake it to ensure there are no air bubbles trapped under the swing arm which would push it upwards (this is probably why the false read even with fresh water).

[hydroid]

Ditto. Spend the money on a refractometer ... you will never regret it.

If you use a hydrometer, get the float type and test the water in a separate container, not bobbing in your tank ... the flow will move it too much.

[dsn112]

I guess even as a newb I should get the refractor. The LFS people said the hydrometer is decent, and I'd be fine.

[marduc]

well you need to do the same thing with LFS advice as you do with the readings on your hydrometer, take it with a grain of salt, and realize that it may or not be accurate, and it is hard to tell when it is, and when it isn't :D

[super stooge]

ive been using the same hydrometer as u and since my tank has been up (only 3 weeks) its given me consistent results of 1.023, i just tested it on fresh water and it sunk straight to the bottom.

am i getting false readings from this?

[dsn112]

any refractor I should be buying? Marine depot has one for 49.99 that looks decent.

[spanglish]

<a href=showthread.php?s=&postid=11045919#post11045919 target=_blank>Originally posted</a> by dsn112
any refractor I should be buying? Marine depot has one for 49.99 that looks decent.

Is it blue?

[marduc]

You definitely want the ATC (automatic temperature compensation) feature, which it appears the marine depot one does have (it looks quite a lot like the one i have :D)

[spanglish]

<a href=showthread.php?s=&postid=11045900#post11045900 target=_blank>Originally posted</a> by super stooge
ive been using the same hydrometer as u and since my tank has been up (only 3 weeks) its given me consistent results of 1.023, i just tested it on fresh water and it sunk straight to the bottom.

am i getting false readings from this?

At the risk of sounding trite, a broken watch is right
twice a day.

While your hydrometer may be accurate (now, or this time)
you'll never really be sure.
Just one really big screw up on salinity will cost you 10 times
the cost of a reliable refractometer.

I really bet if you take a survey of "non newbies" you'll be hard
pressed to find any that disagree.

I am certainly no expert, but an aweful lot of knowledgeable
folks seem to agree on this.

[super stooge]

good point,

time to have a serious look at a refractometer and dig up some cash :sad1:

[dsn112]

no, its black, it seems like its decent though

[Gary Majchrzak]

useful related reading:

http://reefkeeping.com/issues/2004-07/rhf/index.php

[oscarslr]

My hydro meter was off 5 points, as a result I had a salinity of 1.030 yeah spend the extra money, lucky for me i only used it during the cycle

[RyanBrucks]

"My hydro meter was off 5 points, as a result I had a salinity of 1.030 yeah spend the extra money, lucky for me i only used it during the cycle"

I just received my sybon refractometer and got the same results.

previous hygrometer reading was 1.026. Refractometer reads 1.030. I too am only cycling a tank (qarantine tank).

[Coffman34]

I have used a hydrometer sucessfully for the whole life of my tank, about 10 months. You just have to be careful with it. Make sure it gets cleaned. No bubbles when you take readings. And don't rely on it 100%. I have my LFS test my water with their refractometers and it is generally almost spot on -+ .02 at the most. You also have to watch for the diff in temp, the hydrometer will give you a lower reading in hotter water. For instance, when my tank is at 80 degrees, I test my hydro at 1.019, but i know that because of temp it is actually 1.025.

[cloak]

I just don't want to here that the refractometer is off...

[Almondsaz]

Refractometers are easy to calibrate and one of the basic investments in "upgraded" test equipment for a salt water system. Once you start using them you will appeciate their accuracy and ease of use.

[bmrescort]

I could not imagine having to test my water without my refractometer. It is the easiest thing in saltwater to get right. 3 drops of water hold it up to the light and you are done. A refractometer is a MUST.

[wolf pup]

I went for years and years doing FO with a hydrometer. I imagine that there must have been a degree of consistency since I had tremendous success with the tank. I wanted to move into reefkeeping so I bought a refractometer (the marinedepot special) and not only can I rely on its accuracy - it's actually somewhat faster to use. In hindsight, I should have made the purchase many years ago. If you add up any of the other "must haves" for saltwater fish the refractometer winds up being a minimal cost (even the $100 ones) - Just my opinion.

[cd77]

Just an FYI -- My refractometer instructions had me calibrate with distilled water. More than a month later I learned I needed to calibrate it with Salinity Calibration Fluid at 53uS. My refractometer calibrated with distilled water was off by nearly .003 in comparison -- which is very substantial. IMO, if you have a refractometer calibrated with distilled water, you might as well be using a deep six hydrometer.

[mikewise1]

i just found out my hydrometer is 0.030 low also, resulting in high SG. the osmotic shock killed 3 of the mollys i put in to help the cycle. i'll be ordering a refractometer off Marinedepot today too :/

[wolf pup]

cd77 the instructions for my refractomer also stated distilled water. Where are you getting Salinity Calibration Fluid? I would like to be able to do a side by side comparison.

[cd77]

<a href=showthread.php?s=&postid=11048625#post11048625 target=_blank>Originally posted</a> by wolf pup
cd77 the instructions for my refractomer also stated distilled water. Where are you getting Salinity Calibration Fluid? I would like to be able to do a side by side comparison. http://www.marinedepot.com/ps_ViewItem~idProduct~AM1437.html

[Reefer07]

I guarantee there was air bubbles on your hydrometer or something. I have a corallife hydrometer and when I fill it up I just hit on it until there is no air bubbles attached to the swing arm. After that I place it down and take my reading. I have had no problem with my hydrometer as I have checked it MULTIPLE times with my friends refractometer. The hydrometer is almost dead on.
Also, if you don't wash the hydrometer out salt can stay on it giving you an innacurate reading.

[marduc]

<a href=showthread.php?s=&postid=11047286#post11047286 target=_blank>Originally posted</a> by cloak
I just don't want to here that the refractometer is off...

There are a couple of articles that address this issue. A lot of the inexpensive refractometers offered are for salt water (table salt), not seawater, resulting in a slight discrepancy in the SG reading (the already mentioned 0.003).

You can buy calibration standards, or there is also info for making your own with table salt. For calibrating first calibrate the 0 point with distilled water, then check it with a 35 ppt standard.

Refractometers and salinity (http://reefkeeping.com/issues/2006-12/rhf/index.php) - especially note the section titled: Imperfect Refractometer Use: Scale Misunderstanding and Salt Refractometers

the above article also revisits in brief the homemade calibration standard covered in more detail in this article: Homemade calibration standards (http://www.reefkeeping.com/issues/2004-06/rhf/index.php)

[Engine 7]

wolf pup, I have some calibration fluild at my house you can use to do the comparison.

[Owen2thebank]

Why is there very little mention of conductivity meters for measuring tank salinity? Is it because hygrometers and refractometers are cheaper or more reliable? I have access to using a YSI 63 pH/conductivity meter, which reads in micro and milliseimens/cm. It is a very expensive (over $1,000 I think). Should I use this meter or should I buy a refractometer? If I use the YSI then will I need some kind of conversion table? I have been using my swing arm with no problems.

[cd77]

<a href=showthread.php?s=&postid=11062990#post11062990 target=_blank>Originally posted</a> by Owen2thebank
Why is there very little mention of conductivity meters for measuring tank salinity? Is it because hygrometers and refractometers are cheaper or more reliable? I have access to using a YSI 63 pH/conductivity meter, which reads in micro and milliseimens/cm. It is a very expensive (over $1,000 I think). Should I use this meter or should I buy a refractometer? If I use the YSI then will I need some kind of conversion table? I have been using my swing arm with no problems.

A lot of us have temperature compensating digital conductivity or salinity meters -- though I'd imagine most are hobby range in the $100-$150 range :)

Give yours a try! Many of the 53 μS calibration solutions sold online will include a chart.

[Owen2thebank]

I have calibration solutions too, so it never occured to me to buy some at the LFS primarily for the chart. That's a great idea. I'll get some and compare my swing arm.

Thanks for the tip.

[cd77]

$5, includes a conversion chart:

http://www.marinedepot.com/ps_ViewItem~idProduct~AM1437.html

[Owen2thebank]

Your link was very helpful. Marine Depot listed their calibration solution at 53.0 mS. My tank just tested at 54.0 mS.

Thanks