Mixing Salt Water

[Rosco's Reefs]

I am bringing up my new 55G tank and starting to mix water. I am using RO-DI water, using Instant Ocean Salt Mix, and following direction to the T and my water-salt content is too high. Even after lettting it mix for days and making sure the water is at a decent temp it still tests out at 1.032. So:

 

1. Has anyone seen this?

2. Should I not follow the recipe quite as closely

3. How do I get back to equilibrium

 

Thx in advance

[bankyf]

What are you using to test the salinity?

[Big Country]

half cup of IO per gallon usually gets me to around 1.021 and I have to add more salt

Edited February 19, 2011 by Big Country

[Rosco's Reefs]

Just when I think I am learning, I find out it ain't twue!

 

I am using a Instant Ocean Hydrometer and when I tested it again just now it seemed much better, down at 1.021. Makes me wonder what the impact of temperature is on salinity...anyone know?

 

I am asking because it dawned on me that the water in my mixing bucket was warmer than it is now in my tank. I wonder. Thx

[LanglandJoshua]

First of all, with hydrometers it relies on a little arm that swings up and own. When we test our water and dont rinse it out with fresh water salt can build up. That salt can mess up our first reading. I would suggest rinse your hydrometer in fresh water to loosen the arm before testing.

 

Second, waters ability to dissolve material is greater when it is warmer. The science behind it is that when an object is warmer it holds more energy. The molecules move more and take up more space. That even effects the oceans water levels. But when the molecules take up more space, there is also more space between them. For liquids like water this means more space to dissolve things. So warm water will hold more salt than cold. Warm water will also dissolve things faster.

 

I think the solution for too having too much salt in your water is by following the advice of another WAMAS member.

 

"The solution to polution is dilution!" thanks Jim!

 

i.e. add some RO/DI water to it, and retest until your happy. I t can take some time to figure out how much it takes, but you will!

Edited February 19, 2011 by LanglandJoshua

[FearTheTerps]

It could be the temperature, that can effect the SG reading, but that much of a difference I dont think. Most likely it was from using the hydrometer. Those swing arm hydrometer are notoriously inaccurate. Even the tiniest air bubble on the swing arm can make the device give a false reading.

 

What you should use to mearsure SG is a Salinity Refractometer. It will cost about $50 or so, but its really worth it. You can find them online and at your LFS, just ask if you dont know what it looks like or where they keep them.

Edited February 19, 2011 by FearTheTerps

[LanglandJoshua]

It could be the temperature, that can effect the SG reading, but that much of a differce I dont think. Most likely it was from using the hyrometer. Those swing arm hydrometer are notoriously inaccurate. Even the tiniest air bubble on the swing arm can make the device give a false reading.

 

What you should use to mearsure SG is a Salinity Refractometer. It will cost about $50 or so, but its really worth it. You can find them online and at your LFS, just ask if you dont know what it looks like or where they keep them.

 

 

where are you finding them at $50??? I only seem to find the $100+ ones....

[FearTheTerps]

Here's one on aquacave for 60, this is the one I have. When I bought mine( a few years ago) it was onsale for $35

 

http://www.aquacave.com/sybon-salinity-br-refractometer-with-atc-1901.html

Here's another for 50

http://www.aquacave.com/vertex-salinity-brrefractometer-with-atc-2560.html

Edited February 19, 2011 by FearTheTerps

[LanglandJoshua]

wow...ok now I have to order one!!

 

what is the difference between the two refractometers?

[FearTheTerps]

Probably not much. May even be the same manufacturer with a different sticker on it. The sybon comes with calibration fluid, looks like the other one does not. The calibration fluid is just ultra pure water, but my RODI water tests the same as the claibration fluid.

 

Here I am promoting a online store when I said all those things about buying local today.

Local stores should have them for close to the same price, but not really sure, as I have had mine for a few years already and had no need to look at them.

[Chad]

I second the motion to get a refractometer. But if that isn't in the cards right now, I would take the reading with the hydrometer at least three times after getting all the little bubbles off by flicking it with your finger a bunch of times... If the numbers are within about 0.001 from each other, that is what I would call it, otherwise I would continue measuring until I had a good idea what it was.

 

And, FYI, here is a chart that shows the temperature / salinity relationship.

Edited February 19, 2011 by Chad

[flowerseller]

Try Fins & Feathers. I hear they're about $50 for WAMAS members and maybe $60 if not. No shipping.

[hypertech]

You should always calibrate a refractometer with 1.026 solution before using it. It only needs to be done once so make sure you buy it from a place that does it for you or it comes with the solution.

[Origami]

If you mix IO according to the directions, salinity will be in the area of 1.021 to 1.023, so you've either mixed incorrectly or are measuring incorrectly when you get a measurement that's so far off.

 

Joshua gave you a generally accurate statement above: Solubility of many solids in water is greater at warmer temperatures. This does not apply with all materials or with gasses, though. For example, calcium hydroxide (kalk) has greater solubility at lower temperatures than at higher ones. The same goes for CO2, O2, etc. Just a nit.

 

You should use a refractometer instead of a hydrometer. You'll have better accuracy and repeatability. If it's temperature compensating, you shouldn't need to calibrate it for every use. In fact, unless I'm suspicious, I only check mine from time to time. If you use a swing-arm hydrometer, you really need to make sure that you get any air bubbles that may be hanging onto the swing arm off. Also, temperature does affect the specific gravity of salt water (that's what a hydrometer measures: sg), but it's insignificant in our application. If interested, you can find out more about how to use a hydrometer, and how it works here: http://reefkeeping.com/issues/2004-06/rhf/index.php You'll have to scroll down about 3/4 of the way through the paper.

[CaptainRon]

I bought a D-D Aquarium Solutions refractometer. Supposedly they take into account "other stuff" in seawater versus just measuring salt like most refractometers are supposed to. BRK carries the D-D one. I also found it from some Ebay seller. It's not my account and I make no money from it.

[Origami]

If you calibrate your refractometer with a reference solution that is at or near the target salinity, you'll be fine with most any refractometer that we use in the hobby, whether it's the cheaper brine units or the more expensive ones that have scales calibrated for sea water (such as the D-D ones). If you want to calibrate it using distilled or RO/DI water, it's best to have one that's been designed for seawater and not brine.

[Halcyon]

This is a slightly different tact...Depending on the size of the measuring cup (1/2 cup) becase they do differ from style and manufacturer, does any one know how much a true /2 cup of Instant Ocean Sea Salt weighs. I have used a variety of 1/2 cup measures and have accurately measured the water (by weight) but come up with a different salinity each time.

 

 

[gmubeach]

Ebay special:) I ran a group buy for them when I needed a new one, he was very friendly and welcomed the group buy. I don't care where the refracotmeter comes from, BUT I highly recomend using one the fish stores that sell the hydrometers test them against a refractometers.

[Origami]

This is a slightly different tact...Depending on the size of the measuring cup (1/2 cup) becase they do differ from style and manufacturer, does any one know how much a true /2 cup of Instant Ocean Sea Salt weighs. I have used a variety of 1/2 cup measures and have accurately measured the water (by weight) but come up with a different salinity each time.

I thought it was written on the panel how much the 1/2c weighs.

 

I never worry about the kind of accuracy you're talking about when mixing up my change water. Instead, I measure out my water in my change container (a 44G brute), turn on the circulation pumps, and add 1 cup of I/O for every 2 gallons of RO/DI added. This brings my salinity up close. I then add more salt, testing with a refractometer until I'm at 35 ppt. Always allow enough time for the salt to mix up, otherwise you're likely to overshoot your target salinity.

 

Also, always add salt mix to the water, not the other way around. If you add water to the dry salt mix, they'll be a reaction that precipitates out some of the salts, resulting in loss of both salinity and soluble minerals.

 

If you leave your pumps off, over some days the water stratifies, so you should mix it before taking a salinity reading.

[Guest thefishman65]

I know the swing arm Hydrometer have issue. What about the floating ones (I think they are still Hydrometers) with lead shot in the bottom? I know the miniscus (?) can make them hard to read, but is there anything else? Thanks

[Origami]

I know the swing arm Hydrometer have issue. What about the floating ones (I think they are still Hydrometers) with lead shot in the bottom? I know the miniscus (?) can make them hard to read, but is there anything else? Thanks

I've not used these but, as I recall, (as with any hydrometer) you have to ensure that you've compensated for temperature effects if you want an accurate reading.

[BowieReefer84]

Just when I think I am learning, I find out it ain't twue!

 

I am using a Instant Ocean Hydrometer and when I tested it again just now it seemed much better, down at 1.021. Makes me wonder what the impact of temperature is on salinity...anyone know?

 

I am asking because it dawned on me that the water in my mixing bucket was warmer than it is now in my tank. I wonder. Thx

 

 

May have been said, but make sure there are no small bubbles on the arm. This will cause a higher reading...

[LanglandJoshua]

For now I am using a hydrometer with the floating arm. I like to rinse it with fresh water before using it, and shaking it around helps get rid of bubbles. But as soon as I can I am getting a refractometer!

[Chad]

I've not used these but, as I recall, (as with any hydrometer) you have to ensure that you've compensated for temperature effects if you want an accurate reading.

 

This is true. I still have (although I use a refractometer these days) the hydrometer that I got 20+ years ago... a two foot long glass instrument that required about a quart of water to fill the testing tube. They can be pretty accurate, but either need to be used in the temp range they are calibrated for or temp corrected (I think mine is 76 or 77 or something close... I never did the calculation since it was "close enough"). These instruments also vary a great deal in accuracy based on how "nice" they are, and usually larger is better here.

[LanglandJoshua]

Unfortunately as Mrs. Gerbassi, my old oceanography teacher learned. Although the larger is better, its still glass, and VERY breakable...which would be why I think 99.9% of us would rather refractometers. But if you want something sciency for decorations, they would work great