Fluctuating salinity

[Midway11]

Hi there, i just setup a 55 gal salt water tank. When I filled my
tank my salinity levels were where they suppose to be 1.022.
Now after i put my live rock in yesterday, I let it run all
night and when I tested it again this morning, they were way too
high. Are the live rocks doing this? I did a couple of water
changes and I have not been able to get my gravity to the right levels again.
Any advices what can be done to correct it?
Thanks.

[Tuscaquatics]

You have to account for evaporation that occurs. Pure water evaporates from the tank, leaving salt behind. Because of this you have the same amount of salt in a smaller volume of water, thus creating a higher specific gravity.

To counter this you add fresh water every day to top the tank off and keep the salinity normal.

With that said, you want to keep your specific gravity at more like 1.024-1.026.

[Midway11]

Thanks for the advice. I will for sure do that from now on.
Another question would be, in estimate, how long
would I have to wait to test the salinity after adding more salt or
or adding fresh water?

Thanks very much!!

[Tuscaquatics]

First of all, don't add more salt directly to the tank. Mix it up in water first. You should wait at least 10 or 15 minutes before testing again. The longer you wait, the more guaranteed you'll be of an accurate reading.

[juicesay]

Sometimes salt evaporates from your system as welll.

You should just always ATO with RODI instead of freshly mixed saltwater.

Cheers.

[Frick-n-Frags]

you cant evaporate so much water to raise your salinity through the roof in one night.

if the LR was wet live rock..it didnt bring in a bunch of salt..maybe crusty dried LR has enough dried salt on it to raise the salinity tho...


i would strongly suspect the hydrometer/refractometer or the reading techniques.

maybe a second opinion via a differnet hydrometer/refrac that is known to be calibrated and accurate will turn up answers

[Indymann99]

here is a trick that I use. (if you dont have a ATO)

Get your tank at the salinity / SG that you want 1.024-26. mark the water level in your sump(return section) or DT (if you dont have a sump).

Now when the water level drops each day (evaporation), you just top off with FRESH RO/DI to the line you marked and you will be back at your desired salinity/SG.

I would highly recommend you invest in a ATO (automatic Top Off) system to reduce the salinity fluctuations. These systems are pretty inexpensive or you can DYI a system with many plans available here on RC (search ATO in the DYI forum).

hope this helps. I use a JBJ ATO system (pretty inexpensive) that uses a float in the return section and a small pump in a container that holds about 3-4 days of RO topoff water.