View Full Version : Salinity keeps rising
kysard1
07/20/2007, 04:06 PM
I can't understand how my salinity keeps going up. I am using a refractometer (temp compensating), keeping the return section of my sump at the same level.
Every week my salinity goes up from 1.025 to 1.028. I am using RO/DI with a TDS of 3 for top-off. The tank is only a month old so no additives or kalkwasser.
Could it be salt leaching out of these newer liverock?
hubris007
07/20/2007, 04:08 PM
It goes up if the water level is the same, or it goes up if you test it just before topping off?
virginiadiver69
07/20/2007, 04:10 PM
Are you topping off with saltwater?
mr_o98
07/20/2007, 04:19 PM
If you are topping off with saltwater then that is why your salinity is rising. You need to top-off with freshwater, as salt does not evaporate.
ACBlinky
07/20/2007, 04:28 PM
<a href=showthread.php?s=&postid=10381161#post10381161 target=_blank>Originally posted</a> by kysard1
I am using RO/DI with a TDS of 3 for top-off.
That's truly strange - if you're topping off with RO/DI and the water level isn't changing, you're not adding anything, then I have no explanation for why SG would go up by 3 points in a week.
MalHavoc
07/20/2007, 06:25 PM
Here's a point. Do you clean your refractometer very well before using it? If you use it, and then put it away wet, the salt water on it will dry, leaving the salt behind. The next time you use it, your first test will read high, because the drops you add will mix with the salt on the refractometer. Make sense? Make sure it's really clean.
Also, if you use an eye dropper to take water from your tank to test, rinse it well a few times in the tank to make sure there's no dried salt in it. Same reason.
kevin2000
07/20/2007, 09:41 PM
Salt doesn't evaporate .. water does ... tank salinity increases over time unless you replace the evaporated water with fresh (no salt) water -- common problem/simple solution.
EDIT:
Once you get your tank to the proper salinity ... make a mark at the water line and when the water goes lower than the mark you can add fresh water up to that line ... this will insure that your salinity will stay reasonably stable.
Aquarist007
07/20/2007, 10:06 PM
in any case just to make sure do a 20 per cent water change-with salt/ro water that has sat for 24 hrs with a powerhead and heater in the bucket for 24 hrs---
Mix up the salt water in a large plastic garbage can--check the salinity---let the power head and heater run for 24hrs--recheck the salinity level.
kysard1
07/20/2007, 11:10 PM
but I my first post made two important points:
1. I top off to the same level in the sump
2. I top off with RO/DI TDS of 3
monicaswizzle
07/20/2007, 11:24 PM
Well, it is a bit of a mystery, but here are two thoughts--
1) If the salt mix you are using isn't fully dissolved when you add the salt water to your tank, it might have a slight rise in SG as the water sits just because more things disolve into it. Hard to imagine that happening unless you mix up the Saltwater immediately before you add it, but I have had batches at 1.024 after I mix them that measure 1.026 the next morning.
2) I'll be damned if I can remember my second point, although I do agree with the comments Jason made about keeping the measuring tools clean.
3) This wasn't my original second point, but do you have anything else in the tank that could be dissolving/leaching salts into the water? I wouldn't think LR is likely to do that, but if you had, say a hunk of salt as a decoration or something like that. I can't really imagine what would leach or dissolve at that rate and not be visably deteriorating, but maybe you have some cute diver decoration from some other tank that is absolutely packed with dried salt and you didn't notice it, or something crazy like that.
Good luck!!
uscharalph
07/21/2007, 02:12 AM
My vote is with cleaning the refractometer carefully before and after each use.
Young Frankenstein
07/21/2007, 05:33 AM
<a href=showthread.php?s=&postid=10381910#post10381910 target=_blank>Originally posted</a> by MalHavoc
Here's a point. Do you clean your refractometer very well before using it? If you use it, and then put it away wet, the salt water on it will dry, leaving the salt behind. The next time you use it, your first test will read high, because the drops you add will mix with the salt on the refractometer. Make sense? Make sure it's really clean.
Also, if you use an eye dropper to take water from your tank to test, rinse it well a few times in the tank to make sure there's no dried salt in it. Same reason. That's why i personally don't believe in refractometers...
Gary Majchrzak
07/21/2007, 05:35 AM
<a href=showthread.php?s=&postid=10381161#post10381161 target=_blank>Originally posted</a> by kysard1
I can't understand how my salinity keeps going up. I am using a refractometer (temp compensating), keeping the return section of my sump at the same level.
Every week my salinity goes up from 1.025 to 1.028. I am using RO/DI with a TDS of 3 for top-off. The tank is only a month old so no additives or kalkwasser.
Could it be salt leaching out of these newer liverock?
when you add livestock are you adding water from the shipping bag to your aquarium?
drummereef
07/21/2007, 08:36 AM
Either the refractometer is dirty or needs cleaning, or you aren't exactly topping off with freshwater the same amount each time. Have you thought about getting an auto top-off controller?
mwwhite
07/21/2007, 10:45 AM
We do exactly what someone else said. We put a piece of blue tape on the sump and know where the water level is -- drops below that we add RO.... Our salinity never changes...
One other thing - has the refractometer been calibrated lately? We ordered the special solution for to calibrate ours.
smcdonn
07/21/2007, 10:49 AM
<a href=showthread.php?s=&postid=10384090#post10384090 target=_blank>Originally posted</a> by 0 Agios
That's why i personally don't believe in refractometers...
:rolleyes: So you don't believe in refractometers?? Let me know what you do believe in?
mikeatjac
07/21/2007, 11:01 AM
smcdonn, I am with you. A swinging arm is as accurate as a refractometer.
superedge88
07/21/2007, 11:06 AM
<a href=showthread.php?s=&postid=10385119#post10385119 target=_blank>Originally posted</a> by smcdonn
:rolleyes: So you don't believe in refractometers?? Let me know what you do believe in?
I believe in God, santa and refractometers!:D
Onesaltydawg
07/21/2007, 11:28 AM
Use a cerified Hydrometer...can t go wrong there
Aquarist007
07/21/2007, 05:54 PM
If you are new to the reef hobby then a refractometer is the less error way to go.
PorFshGuy
07/21/2007, 06:14 PM
If the tools you use to measure the salinity are in question then take a sample of the water to the local fish store and have them test it there.
jdjeff58
07/22/2007, 09:57 AM
<a href=showthread.php?s=&postid=10381161#post10381161 target=_blank>Originally posted</a> by kysard1
I can't understand how my salinity keeps going up. Every week my salinity goes up from 1.025 to 1.028
If this is a weekly thing, then I'm assuming that you have to add enough water to get it to drop back to 1.025? If that's true, your rate of evaporation is higher than your rate of replacement of water.....assuming the refract. is calibrated properly.
I agree with the proper rinsing of the refract and the eyedropper. I rinse mine with DI water and wipe the glass clean. Also, with ATC it is important to wait at least 30 seconds before taking a reading so the temp filament can adjust itself.
I'm not sure if you have a skimmer in your sump. I have found that the skimmer effects the level of my sump. The more water the skimmer pulls in, the lower the level. If I turn my skimmer off, the level goes up. The funny thing is that when I turn it back on, the level does not return to the same mark. But adjusting the skimmer during the week could be changing the level in your sump....in the return section. It can be a little tricky if your just relying on your level mark.
I have also noticed on water changes that when I mix up a batch of fresh salt water, no matter what I do, and how careful I am with the amounts, there is always an error of some sort when it's all said and done. The level never returns to the same mark and the salinity is off slightly. There is always some tweaking required when it's all over.
I use an auto top off and a conductivity probe. The probe gives me 'real time' salinity readings. But I periodically check the probe against the refractometer. It's good to have a point of reference. With only one instrument, it's difficult to tell where the problem lies. You might want to get the 53ms (1.026 SG) Pinpoint calibration solution for your refract. It's an inexpensive way to verify if your instrument is/is not lying to you.
virginiadiver69
07/22/2007, 10:14 AM
<a href=showthread.php?s=&postid=10390073#post10390073 target=_blank>Originally posted</a> by jdjeff58
Also, with ATC it is important to wait at least 30 seconds before taking a reading so the temp filament can adjust itself.
A Milwaukee rep told me that it was ambient temp not water temp that was being compensated for.
jdjeff58
07/22/2007, 10:53 AM
<a href=showthread.php?s=&postid=10390165#post10390165 target=_blank>Originally posted</a> by virginiadiver69
A Milwaukee rep told me that it was ambient temp not water temp that was being compensated for.
Regardless of the temp being compensated for, it still has to settle out before you read it. The water temp and the ambient temp will most likely be different when you first drop it onto the glass.
virginiadiver69
07/22/2007, 11:09 AM
No it doesn't. As long as the ambient temp stays the same i.e. in your den ( or wherever your tank is) there is no need to do any waiting to read the measurment. In the end, it is a minor fact that was misrepresented but wrong none the less.
jdjeff58
07/22/2007, 11:54 AM
<a href=showthread.php?s=&postid=10390383#post10390383 target=_blank>Originally posted</a> by virginiadiver69
No it doesn't. As long as the ambient temp stays the same i.e. in your den ( or wherever your tank is) there is no need to do any waiting to read the measurment. In the end, it is a minor fact that was misrepresented but wrong none the less.
YOU do what you want. I'm trying to help someone get an accurate salinity reading.
Source: Refracts.com
What is a refractometer
A refractometer is a handheld optical device that measures the concentration of solids in a liquid. A drop of the sample liquid is spread onto the prism. Light reflected thru the sample, into the prism is reflected onto the scale inside the instrument. Viewing the scale thru the eyepiece, the reading is taken at the division of the blue and white reflected light. Common liquids to sample are fruit juice, sugar concentrations, salt water, urine, and coolant.
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How do I calibrate my refractometer?
Refer to your refractometer operation manual. If you do not have a manual, the following instructions will give you basic knowledge of the calibration procedure.
Open daylight plate, and place 2-3 drops of distilled water on the main prism. Close the daylight plate so the water spreads across the entire surface of the prism without air bubbles or dry spots. Allow the sample to rest on the prism for approximately 30 seconds before going to step #2. (This allows the sample to adjust to the ambient temperature of the refractometer)
Hold the daylight plate in the direction of a light source and look into the eyepiece. You will see a circular field with graduations down the center (you may have to focus the eyepiece to clearly see the graduations). The upper portion of the field should be blue, while the lower portion should be white.
While looking into the eyepiece, turn the Calibration Screw until the boundary between the upper blue filed and the lower white field meet exactly on the 0.0°. Once complete, the instrument is calibrated for your current ambient room temperature. When working temperature of the room or environment (not the sample) changes by more than 5°F, we recommend recalibrating to maintain accuracy and reproducibility.
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What is ATC?
ATC is an abbreviation for automatic temperature compensation.
Automatic Temperature Compensation allows the user to take scale readings at various ambient room temperatures. Typically, if the temperature of the room changes by a degree or two, the refractive index shifts and the reading on the scale is not accurate. With automatic temperature compensation, temperatures can shift between 20-50 degrees Celsius.
Temperature of the sample: The sample must be the same temperature as the prism. This can be done by waiting 30 seconds. It is not possible to adjust for the difference between temperature sample and the prism temperature. ATC and non-ATC models BOTH must have the sample at the same temperature as the prism.
Air or ambient temperature of the room: Automatic Temperature Compensation model is best suited for atmospheres where ambient air temperature may change. Smallest changes in air temperature will affect reading. For best results, calibrate your model at 20C. It will automatically slide the scale in the temperature range of
Non Automatic Temperature Compensation model - Calibration is only accurate for the temperature at which calibration was done. If the temperature of the room shifts 5 degrees, you must recalibrate. (even 1 degree affects the scale, so if the measurement is critical, recalibration must be done)
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Ambient temperature vs. sample temperature
Whether you have an ATC or non ATC model refractometer, your sample must be the same temperature as the prism on the refractometer for an accurate reading. If you are working with samples at a temperature different than the ambient room temperature, you MUST leave the sample on the prism for 30 seconds before taking the reading. This allows the sample to acclimate to the temperature of the prism before a reading is taken. ATC does NOT compensate for the temperature of the sample.
virginiadiver69
07/22/2007, 12:52 PM
<a href=showthread.php?s=&postid=10390592#post10390592 target=_blank>Originally posted</a> by jdjeff58
YOU do what you want.
I usually do. ;)
I'm sure everyone appreciates your help but let's try to be accurate.
jdjeff58
07/22/2007, 01:30 PM
<a href=showthread.php?s=&postid=10390850#post10390850 target=_blank>Originally posted</a> by virginiadiver69
I'm sure everyone appreciates your help but let's try to be accurate.
Huh? I refuse to fight with a one armed man.
kysard1
07/22/2007, 03:28 PM
It was the temperature, I made sure my refractometer temp is the same as the water temp, and now I am getting a lower reading.
virginiadiver69
07/22/2007, 03:36 PM
Hey! I resemble that remark...I really do have one arm. :lol:
Either way it wasn't worth picking an argument. :)
jdjeff58
07/22/2007, 06:59 PM
<a href=showthread.php?s=&postid=10391556#post10391556 target=_blank>Originally posted</a> by kysard1
It was the temperature, I made sure my refractometer temp is the same as the water temp, and now I am getting a lower reading.
Good deal...
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