S.g.

If you had a humid room and the tank was a lot cooler than the surrounding environment (aided by an unsealed lid) condensation would form on the lid and drip into the tank which could lower your salinity. You would need to double glaze the tank to stop mass condensation on the sides of your tank.

 

If you do a water change often, all this problems tend to be minimized.


Hug

 

For those that have to use a Hydrometer due to lack of funding,
If you take the Hydrometer and rinse it in warm water then fill it slowly with tank water you will get a more accurate reading than you would just taking it out of the cabinet and sticking it in the tank and filling it quickly ...
Danny

 

I change water reg.... I will have to relate it to the Skimmer as this sound's logical for such a rapid drop....
Danny

 

My room temp is 73 my tank temp is 77 the top is open
Danny

 

Have you compared this to a refractometer's reading to know you are getting a more accurate reading with the hyrdometer?

The problems that doing it this way "fixes" are air bubbles and salt residue. Both of which would give you a higher than normal reading, not lower.



If you just set up your skimmer and are getting a ton of skimmate, then that would be a possibility. But it's not removing huge volumes of water, even if it is concentrated. Additionally, any effect a skimmer would have on SG would be gradual and consistent, more or less, over time. It would not, IMO, explain a sudden and dramatic drop in SG.

The only way I can explain a sudden drop in SG is replacing Water Change water with fresh or any other method of adding additional fresh water volume... or by using a bad measuring device.

Or, maybe you did a water change but didn't mix it and let it sit for a day before you added it back in your tank. It takes a while for the salt to mix, but this usually ends up in raising SG. Just guesing though, not saying this is your actual problem.


I've heard many times the 'lack of funding' thing with refractometers. I'm sure it's very true for many people. But I see a $30 measuring tool that is needed to really care for delicate corals and/or fish, most of which were more than $30 to begin with... So, I say, to those that use a hydrometer due to lack of funding, skip your next couple of coral or fish purchases so you can afford the refractometer. It really is that much better.

 

I did never had any problem with sg because of the skimmer.
I have a 112g and my skimmer is an OCTX-300 (oversized for my tank). I clean it up every week and mine sg is stable in 1.025.


Hug

 

I didnt mean you get a better reading than a refractometer but the hydro will read better if rinsed in warm water than it would without...refractometers are better overall no doubt you misunderstood the writing...