Salinity changes with temperatures?

[longhorn_20m]

Okay I set up my tank last night, and the overflow I had was pretty loud, so I added water to that sump side to where when it overflowed isn't as loud. Well I had the right salinity before I added water, and I mixed up a batch, but I used a little hotter water so the salt would dissolve better. I got it to the right salinity and added it to the tank. This morning when I woke up the salinity was lower, around 1.010, not the usual 1.024. As the temperature raises, does the salinity raise too? Or did I do something wrong? Today when I get home from school, I'm gonna take some water out, and add more salt, and add back till I get salinity back up. Let you know what happens, just wondering if temperature affects the salinity?

[R.Allard]

Might want to check this, but im sure you shouldnt add hot water from your tap to your tank . It has to many metals and buildup from the waterheater may affect your water quality..just a thought!! :grin:
R.

[longhorn_20m]

Well got home from classes, and I don't like it when things are n't done and I don't want to wait, just want to know the salinity is right. So I took water out, added salt, and then poured back in. I kept doing this ofver 30 mintues till I got the salinity right. All I have in there is live sand and live rock. So I don't think it hurt anything. Let it run for a few days, then gonna add some more live rock. I need to get the final lighting before i'm gonna add anything coral wise.

[captexas]

What are you using to measure your salinity?

If you are using a plastic swing-arm style hydrometer, they can be inaccurate at times. Small air bubbles can cling to the arm causing it to raise higher. If you are using tap water (which is not good) the metal ions and junk in the water can cling to the arm and bring it down. Also remember you should always rinse it out and let it dry after each use. As far as using the hot water, those plastic hydrometers are usually intended for use between 68 and 85 degrees so that could have also affected your results. When I had one, I would always take several measurements to get an average reading.

If you are using a refractometer, make sure it is properly calibrated based on the instructions that came with it using distilled water only. Some refractometers have automatic temperature adjustment and some don't. If your unit does not, you must always adjust the water to the correct temperature before taking a reading.

Hope that helps,
Chris

[matt]

I agree with Chris here; There is practically no way you could have changed your SG from 1.024 to 1.010 by rasing your sump level with hot water. If your readings were that far off, there's definitely something wrong with your hydrometer. Remember this: 1) hydrometers, plastic or floating, measure specific gravity which is temperature dependent, but not anywhere near enough to account for that kind of difference. Salinity is measured in PPT, nat seawater is usually around 35PPT. Thats parts per thousand. A salinity of 35PPT has a S.G. of around 1.025 at 77 degrees, or soemthing like that, I can't remember exactly. Heat the water to 84F, you're looking at around 1.023, or something like that. So the difference is not that great.

2) Plastic swing arm hydrometers are notoriously innacurate, sometimes off by .005 or more.. like reading 1.025 when your actual S.G. is 1.020. That is significant. The only way to get around it is to buy either a refractometer or a big glass floating hydrometer that's lab quality, and use it at the right temp.

HTH
Matt

[longhorn_20m]

I'm using a floating one. I used the majority of RO water. But the overflow was loud and I didn't have any water left to bring the water level up to quiet it down. So I used some warm tap water. Hopefully this won't hurt anything. All seems well. I have something on one of the live rocks. A polyp or soemthing that is out and looks fine. I will try adn take a picture of it to figure it out.

Hopefully in a week or two can start adding stuff. My salinity level is fine now, just checked it and looking good.