Salinity vs Temp

[Sytje1234]

Just a quick question :hmm2: From what I've read....I think....Salinity (SG) changes with temp. Correct?:D. Say you have a temp in your tank of 77/78 degrees and you set your salinty to this temp with a 1.026. Temp rises to 82...what is your salinty going to change to? Farley.....I know you going to know the answer to this...:lol2: So...I guess my real question is "What is the best temp to set your salinty to.. with temp fluctuations in the tank?" The colder the tank, the salt will condense, the warmer the tank it will disperse more? Right? Wrong?

I let my tank fluctuate between these two figures : 77 & 82 basically on it's own. It does have a heater in it that's set. Usually in the morning the water is cooler, in the afternoon it is warmer....probably because of the lighting coming on. So much for heaters.....I have air conditioning in the house which keeps the temp down below the :uhoh2: temp during the summer. All inhabitants are happy. Just wondering....

[disc1]

Specific gravity and salinity are two different things. Specific gravity changes with temperature, but salinity doesn't. It matters what the salinity is in the tank, but the specific gravity moves with temperature just like it would in the real ocean. Specific gravity is really just a surrogate measure for salinity.

Since the conversion from specific gravity to salinity depends on temperature it's not the temperature of the tank you are worried about but the temperature of the water when you measure it. If you are using a hydrometer, then they are calibrated to work at a specific temperature, and you need have the water close to that temperature when you measure it but it doesn't matter that it was a different temperature in the tank.

If you're measuring with a refractometer, then it's even simpler. A refrac tells you specific gravity and salinity, but actually measures neither of those. It measures refractive index. The refractive index also changes with temperature, so the refrac is calibrated to a certain temperature and the refrac needs to be at that temperature when you make the measurement. The drop of water on the refrac will come to the same temp as the refrac pretty quickly, so again it doesn't matter what it was in the tank. Most good refractometers have automatic temperature correction (ATC). That means that for the range of normal room temperature, the refractometer will adjust it's calibration by itself.

[cloak]

My tank runs between 76-85 throughout the year. (20 gallon) I've never had any problems with salinity/SG due to a variation in temperature. The floating glass hydrometer I have works just fine. ~1.026

[Andrew]

One will not affect the other. The temperature of the water can not determine the density of salt content of the tank. I'm not sure who's book your reading or who told you that but they are crazy.

[Sytje1234]

:cool: & awesome. Thanks for getting back to me....I'd been thinking about that for a long time recently and how all that works. Some of us noobies are probably clueless and I am one of them on purposes of individual matters in a tank and how they all interface with each other. It can get :confused::) Normally I try to run my test at the same time of day, and I was also told by someone at a LFS not to test your parameters when you been messing with the tank and stirring up the sand and everything else because the readings can be false. Is that true?

[Sytje1234]

One will not affect the other. The temperature of the water can not determine the density of salt content of the tank. I'm not sure who's book your reading or who told you that but they are crazy.

Definitely not on RC...that's why I come and ask all of you. I know that you all are very knowledgeable and have done reefkeeping for years..:dance: It's like "when in doubt, check it out" and this is where I come for answers. If I'm questioning something, I know I can always get great answers from RC. Glad there is a web site on saltwater tanks as awesome as this. :thumbsup: Thanks, eh?

[Andrew]

Granted Ice is less dense than 80 degree water but you're talking about a 5 degree difference in our tanks, salinity would not be affected even with an accurate refractometer.

[disc1]

One will not affect the other. The temperature of the water can not determine the density of salt content of the tank. I'm not sure who's book your reading or who told you that but they are crazy.

Density and temperature are directly related. Rising temperature lowers density. That is absolute fact.

You're probably right on that over the typical range of fish tank temperature, the effect is pretty minimal.

Here's one of Randy's articles that sheds a little light and links to some others.

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

[sponger0]

The max saturation a liquid can dissolve can be affected by temperature but it would have to be more than a 5 degree difference. I would think it would have to be a 10 degree difference or more in order for it to affect the amount of salt that can be dissolved in water.

[Meanmike]

I recently purchased this salinity monitor and am wondering if it was a good choice. http://www.bulkreefsupply.com/store/american-marine-pinpoint-salinity-monitor.html I have only ever used a hydrometer in the past but am currently taking my setup to the next level.

[Sytje1234]

That's it! :bounce1: Those are some key words...Specific gravity and salinity are two different things! All this time I have been thinking SG, salinity, and salt were all the same things. :crazy1: Wow! Thanks for all of you making that clear. Wow! :cool: I took biology in college and high school. Over time, it's amazing how much you forget. I guess.....more :reading: & :reading: Very interesting!

[Meanmike]

I recently purchased this salinity monitor and am wondering if it was a good choice. http://www.bulkreefsupply.com/store/american-marine-pinpoint-salinity-monitor.html I have only ever used a hydrometer in the past but am currently taking my setup to the next level.

Anybody? I didn't want to start a new thread just for that question.

[disc1]

Anybody? I didn't want to start a new thread just for that question.

But you should.