How high a salinity is too high?

[drsyme]

I just got a pinpoint salinity monitor today. Just calibrated it, new battery. And it reads a S.G. of 1.0317!

Who knows how long it has been that high. My hydrometer has been reading 1.0235 all along, not temperature corrected.

Everything in the tank is fine. Could they be used to it? Is the reading off?

Do I need a refractometer?

[tdwyatt]

Don't make any sudden changes, in particular if the inhabitants look fine. Keep in mind that the salinity meters may measure all the ions in tank water for salinity measurements as a function of the ability of the water column to measure conductance. This is usually fine if we are talking about natural seawater, as it is normal conservative for most of the elements that affect salinity.

In our ASW, we supplement a number of substances, some of which are way above what is normally found in seawater (i.e., Calcium and Alkalinity), although I don't see how they could drive it quite that high.

Before you make any sudden major changes, borrow or buy a refractometer, as most of the swing arm hydrometers like the one you were using before might be off a little, but not quite that much. Since this is a new instrument, don't jump off the deep end and make any major changes until you can confirm the accuracy (even with recent calibration) of the salinity meter.

I am not a big fan of the salinity meters, as there are just too many things that can skew the results, but they are nice to have to give you an indication that something might be wrong with just a passing glance. With that said, I must add that I do not own one for the reasons already posted above; a nice gadget, but they are not all that... A temp-corrected reading from a bulb hydrometer with an internal thermometer would be the most accurate measurement (if you buy a quality one), also up there are the refractometers, and they are much easier to use than a fragile glass bulb hydrometer. I DO have both of these. The upshot is don't rely on just one measurement, especially if you suddenly get some way out of range results and the critters look fine.

On where would there be problems with salt, Red sea organisms routinely see 40 plus PPT salinity and must occasionally endure local hot spots of salinity (this corresponds to SG of 1.030 at 80 degrees F), so I wouldn't get too bent out of shape just yet. If you find that your salinity is indeed this high, the key to good recovery is to VERY SLOWLY DILUTE THE TANK (assuming 75 gallons tank volume) by taking out a few quarts of SW each day and replacing them with fresh water. In this manner, the salinity is gradually reduced over several days (may need more or less seawater to water change depending on tank size).


If the critters look good, then there is no need to do anything until you can confirm the results for the salinity. Confirm the numbers and act accordingly.


HTH, just out of curiosity, what does the meter read for distilled water?

[wharyat]

Does it say anywhere that the meter needs calibrated?

Isn't it odd for a hydrometer to be that far off?

Tom, what are your opinions on glass hydrometers?

[drsyme]

My RO/DI measures 1.1 on the salinity meter. That is with the inline TDS meter reading 1 ppm.

I was not planning on making any drastic changes. I was hoping that it would corroborate my hydrometer, and let me see changes at a glance, but I was also hoping to use it to correct they salinity of my water change water.

[Spridle]

Here's my experience with a refractometer, electronic conductivity meter and swing arm hydrometers:

In my tank, I had readings of 1.019 and 1.023 with two different swing-arms. The conductivity meter also said 1.023.

I bought a refractometer that said 1.020 for my tank water. I then got a sample of natural seawater on the beach in Ft. Lauderdale, Florida a few weeks ago and the refractometer reads 1.026.

I have concluded that the refractometer gives the best measurement. Over the past 2 weeks, I have increased the salinity to 1.024 using the refractometer readings.

[BigDaddy]

To add to the salinity questions: I'm trying to figure out why my specific gravity would be going up... I don't add anything... only straight RO water for top offs yet my sg measured by one of those instant ocean hydrometers has been going slowly up from 1.022 and now it's up to 1.025ish. (??)

[tdwyatt]

Originally Posted by wharyat

Does it say anywhere that the meter needs calibrated?

Isn't it odd for a hydrometer to be that far off?

Tom, what are your opinions on glass hydrometers?

Yeah, my thoughts on the swing are hydrometer as well. Sometimes there might be a few bubbles sticking to the swing are of that type of hydrometer, but a few taps will usually dislodge them. I use the swing arems while mixing asw in a barrel, then make my final check/adjustments with a refractometer.

If I want to be really exact, I use a lab-grade bulb hydrometer with a thermometer in the hydrometer. This allows for exawct SG and temp of the device so that you can make temperature corrdctions. I usually use this to check calibration of my refractometer, but I have been known to use it to mix a batch of water or to check the tnk from time to time.

Ultimately, the bulb hydrometer with temp correctioin is the most accurate, although it is almos the most time consuming to use (allow for temp equilibration between bulb materials and the water column, analog measurement vs gradient-fixed calivbratiion in ATC refractometers, etc)

Originally Posted by drsyme

My RO/DI measures 1.1 on the salinity meter. That is with the inline TDS meter reading 1 ppm.

Jack, I am already concerned, as if the salinity meter were accurate, and the reading is in terms of the SG of the sample, it would measure distilled water at 1.000 SG, although I don't use these meters, so it may be that this is a limitation of the device. If it is the SG, then I would expect that it is already starting off with a hypersaline reading at 1.1 . If it is 1.001 SG for Distilled water, that is not enough error to be significant for our purposes and may actually reflect an issue with the distilled water.

BigDaddy: How are you doing your topoffs? What about your Calcium and alkalinity supplements?

[drsyme]

Originally Posted by tdwyatt

Jack, I am already concerned, as if the salinity meter were accurate, and the reading is in terms of the SG of the sample, it would measure distilled water at 1.000 SG, although I don't use these meters, so it may be that this is a limitation of the device. If it is the SG, then I would expect that it is already starting off with a hypersaline reading at 1.1 . If it is 1.001 SG for Distilled water, that is not enough error to be significant for our purposes and may actually reflect an issue with the distilled water.

The MONITOR reads 1.1. That is in mS. Whatever that means, I dont know what those units are.

But according to the chart 1.1 mS is .9994 SG (or slightly over that).

So that seems close, huh?

http://www.americanmarineusa.com/sal...onversion.html

[drsyme]

Originally Posted by tdwyatt

Yeah, my thoughts on the swing are hydrometer as well. Sometimes there might be a few bubbles sticking to the swing are of that type of hydrometer, but a few taps will usually dislodge them.

And I usually tap my swing arm hydrometer. Wouldnt the bubbles tend to make the SG appear higher than it actually is? I thought they made the swing arm lighter (raised it) relative to the water. (Assuming bubbles are usually on the long part of the arm.)

[drsyme]

This morning the meter was reading 61 so down slightly. That is with only some top off water to keep the level stable. But even with that the rate of the top off was a little slow so the level in the sump was down slightly, which should usually equal a higher SG.

The other interesting thing, is that, (I have kalkwasser in the top off water) I am getting some calcium carbonate precipitation on the tip of the top off device (it is in the water) and some other precipitation along some tubing in the sump near the top off. (There is also a heater there). Last check calcium was 410 and alk was 3.3. I will check again tonight.

[Nabber86]

DRSYME,

Your salinity meter is really a "conductivity" meter and is reporting in microsiemens (mS). 1.1 mS is a very low number and would be indicative of water with extremly low dissolved ionic compounds and Specific Gravity near 1.0. Sounds like RO/DI water to me.

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Spridel,

How did you determine that your refractometer gives the best measurement? You took a handful of readings using several different methods and got varying results. This sounds normal to me. You have to compare the readings of the of each of the methods with a known standard to determine which one gives the best readings.

Not trying to pick a fight or anything.

[drsyme]

Originally Posted by Nabber86

DRSYME,

Your salinity meter is really a "conductivity" meter and is reporting in microsiemens (mS). 1.1 mS is a very low number and would be indicative of water with extremly low dissolved ionic compounds and Specific Gravity near 1.0. Sounds like RO/DI water to me.

Ummm, Nabber86. Thanks for the info on what the mS stands for.

But, I was aware it was a conductivity meter. And I am aware that 1.1 is low. In fact this WAS the reading for RO/DI because Tom was curious about what the monitor was reading RO/DI. I posted the link to the table to convert mS to SG, and 1.1 = .9994 SG.

[Nabber86]

Well then I guess we agree. I thought somebody was questioning the 1.1 reading as being hypersaline.

FWIW - your TDS meter is proly a conductivity meter as well (calibrated to output ppm).

[drsyme]

Originally Posted by Nabber86

Well then I guess we agree. I thought somebody was questioning the 1.1 reading as being hypersaline.

FWIW - your TDS meter is proly a conductivity meter as well (calibrated to output ppm).

Yes they are both conductivity meters, with different units. I suspect because the TDS meter is for water that is close to 1.000 SG, and the salinity monitor is for reading high conductivity salt water, with a SG of 1.025 or so. You calibrate it with a 53 mS solution.

Honestly, I was not quite sure what Tom was getting at in his comment about the hypersaline solution. I expected that he and I had some confusion about what the meter's readings were. He might have thought that when I said 1.1 I meant a SG of 1.1, and I was just clarifying that the reading in mS was 1.1.

[wharyat]

I'm sure Tom thought the SG was 1.1 as did I, that would be hypersaline.

I'm glad to hear about the bulb hydrometers, was wondering if I had wasted money on a "laboratory grade" one.