What causes salinity to rise and is it common?

[kmasonbx]

Just curious as I've noticed my salinity rises. I mix my water and put in the tank at 1.025 but recently I tested the tank and it was at 1.028. I don't have any corals and the fish are doing just fine so it's not a problem just wonder what are the possible causes and if it happens to everybody.

I'm currently using conditioned tap water but I have a RO/DI unit on the way and will be changing out the water. So right now my nitrates and phosphates are high.

[rysher]

evaporation

[Sk8r]

Evaporation. You top off ONLY with fresh water, never with salt unless you are TRYING to raise the salinity.
The mineral content of water does not evaporate. Only the H2O does. Ro/di is pure H2O, no minerals. That's why when mixed with the complex minerals of your salt mix, it becomes pure sea water.
A healthy 55 gallon tank should evaporate about a gallon a day, to be replaced with fresh water.
Eventually, with stony corals, you will supplement lime powder into the topoff fresh water, which will feed the corals. THat's why encouraging evaporation is a good thing. Evaporation also assists 'gas exchange', in which the sandbed 'breathes' nitrogen bubbles back into the atmosphere.

To keep up with evaporation, your tank needs an ATO [automatic topoff] which should be among your first acquisitions. You hook up the float of the ATO, plug it into the wall, plug a small Maxijet into the ATO, and put the Maxijet into a bucket of ro/di that has a small hose run back to BUT NOT TOUCHING! the sump water. Setting up an ATO is how you are able to go away for the weekend without coming back to a tank disaster.

[karsseboom]

well lets think? water evaporates but the salt stays in the water, so the salinity will rasie unless you are toppoing off with freash water. Are you topping off with saltwater? are you not topping off at all?

[Whisperer]

Check your calibration for accuracy. Also, you are referring to specific gravity.

[nadking]

Also make sure the temperature of your water change salt water is the same as the temp of the tank. Different temperatures can throw off specific gravity quite a bit.

[kmasonbx]

Thanks. I was topping off with saltwater. Judging from the salt crystals surrounding my tank that I have to wipe off I made the incorrect assumption that the salt was leaving the tank when the water evaporated.

[Sk8r]

Ah! That's called salt creep. It fakes out a lot of people. It's not really a lot of salt---just looks like it. It gets on everything. That's ok, I had to ask that question when I first started!

[karsseboom]

Thanks. I was topping off with saltwater. Judging from the salt crystals surrounding my tank that I have to wipe off I made the incorrect assumption that the salt was leaving the tank when the water evaporated.

wow! glad you came here and worked it out...

[TellyFish]

Lol, I did the same thing when I first began! You picked the right place to ask for help.

<a href="http://s1184.photobucket.com/albums/z332/tellyFish/?action=view&amp;current=salinityDemotivational.jpg" target="_blank"><img src="http://i1184.photobucket.com/albums/z332/tellyFish/salinityDemotivational.jpg" border="0" alt="Photobucket"></a>