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aquaman05
10/11/2010, 01:03 PM
My tank is in cycle mode now going on 3 weeks. Its a 75 gallon with a 20 long sump/fuge. I have been watching the sump and the water level seems to be dropping alittle every day. So i just put in RO water until its back up to what i think is the normal level. But last night i checked my salinity and it seems to be dropping. Im guessing this is from the top offs.
Should i be topping off with salt water ?

Thanks for looking

thegrun
10/11/2010, 01:20 PM
No, top off with ro/di water, salt does not evaporate. If your salinity is dropping, you must be:
1. Measuring your salinity incorrectly, are you using a calibrated refractometer to measure salinity?
2. Pulling salt water out of the system and replacing it with ro/di water (changing filters...). Not a likely cause.
3. Temperature fluctuations in the water will cause slight variances in salinity, most refractometers have a built in compensator.

njudson
10/11/2010, 01:21 PM
You are right to be topping off with RO water. How are you measuring salinity? is the temp staying constant?

aquaman05
10/11/2010, 01:26 PM
Im am using a hydrometer.
My temp was going from 78 to 80 but i think its been staying at 78.5 the last week and a half.

Im not taking any water out just putting more in. The lights have been off other than maybe 1 hr a day just to look around and perform some testing. Skimmer has not been running either.

mgoblue
10/11/2010, 09:22 PM
Have you marked a line on the outside of your sump that tells you where to top off to? That would help to be more consistent with the top off, but it doesn't seem that it would throw it off much. Once you get the salinity where you want it, I would mark the sump level with a sharpie or a piece of tape so that you can always top off to that exact point.

capecoral
10/11/2010, 09:25 PM
Gotta love the sharpie lines that save the day...

cornraker
10/11/2010, 10:04 PM
Idk if this is your case, but salt creep lowers my salinity ever so slighty

ccolt1
10/11/2010, 11:25 PM
I was wondering that myself? So just us RO water and know salt? Thanks

steelhead77
10/11/2010, 11:41 PM
Idk if this is your case, but salt creep lowers my salinity ever so slighty

Say what?? You cannot possibly have enough salt creep to measurably lower salinity.

aquainas
10/11/2010, 11:46 PM
Buy yourself a good refractometer it will be well worth it:thumbsup:

aleonn
10/12/2010, 02:20 AM
I got my refractometer from ebay for half the price of most online vendors. Best value for a necessary tool.

lordofthereef
10/12/2010, 08:11 AM
Are you running a skimmer? That will do it, especially when skimming wet.

Palting
10/12/2010, 08:33 AM
Check your DT water level. Sometimes, and I stress sometimes, the water level in the DT slowly rises as the drains mature and eventually stabilizes. This causes the sump water level to fall, replaced with ro/di water, lowering salinity. Sometimes. My 150 did, my 110 not.

Jstdv8
10/12/2010, 12:56 PM
Are you running a skimmer? That will do it, especially when skimming wet.

I was thinking this too. there's only a few ways to get salinity to drop significantly.
A leaky tank, or a spray bar that is spraying little amounts of water over the side of the sump or skimming wet and not watching it closely.

aquaman05
10/12/2010, 01:04 PM
No skimmer running yet.
I will make me a mark on my sump and try it that way for a few weeks.
No salt creep anywhere yet, only been running abot 2 1/2 weeks

aquaman05
10/12/2010, 01:06 PM
I got my refractometer from ebay for half the price of most online vendors. Best value for a necessary tool.

Can you pm me link please?
Thanks

aleonn
10/12/2010, 01:19 PM
It's been a year since I purchased, but just search for "refractometer" and look at the options. There are also wine refractometers that have a different scale, so keep that in mind.

capecoral
10/16/2010, 07:41 AM
Someone said a tank can slowly increase level over time... how?

shifty51008
10/16/2010, 08:02 AM
I beleive IIRC that dosing mag will over time increase your sg.