Unchanging water salinity??

Ok I'm new here so please go easy on me

I've had my salt water reef aquarium up and running for about 6 months now and up until recently have been using a hydrometer. And I always added clean water whenever topping off the tank. But now that I've bought a refractometer with ATC, I've just noticed the following. I did a water chance about 4 days ago. I keep a normal specific gravity of 1.024. There is probably about 3/4 to 1 gallon evaporated as of now, and my refractometer still reads 1.024. If I top off with clean water, the salinity will drop. This doesnt make a lot of sense to me. I've checked the entire system for leaks and there are none. I've calibrated the refractometer with pinpoint salinity calibration fluid. Any ideas why my salinity seems uneffected as it evaporates?

 

What kind of fresh water are you using for the top off? When you calibrated the unit, did you use the calibration fluid that came with it or something else?

 

I use an AP Tap Water Filter to filter my water. I know its not as good as RO/DI water but I havent had any problems. And supposedly it's a very good filter. As for calibration, I bought the "Blue Refractometer" Model RHS10-ATC and I also got the Pinpoint Salinity fluid (53.0mS) Calibration fluid. Everytime I check the refractometer with the cali fluid, it's right on the money.

 

Does the refractometer give the same reading as the hydrometer? If the refractometer(RM) doesnt, then theres something wrong with it. Could be that its defective or the calibration fluid is no good. Try testing other SW other than yours.

 

How many gallons is your tank? One gallon of evaporation is not much...

 

He has a 36 gal

 

i lose 4-5 gallons in my 55 and it doesnt move......but overall i have 78 total system volume

 

If it is drooping off unless it was significant I'd not worry about it .. Also where do you add the top off to the system and how long after adding the top off water and from where did you take the sample to test ? But I'd not worry about water that much.. I just tested ours last Wed. For the first time since early Dec. It was at 1.024 1.025 ? I blast through over 5 gallons aday to evaporation And when I tested the salinity It was lower the normal as the ATOF had the feed solenoid off . Nothing alive is ever static

 

Skimmer probably accounts for salt loss, that and normal salt creep.

Just add some to topoff water when it appears to be lowering significantly.

That, or let it be cue to do water change.

:-/

 

I guess the protien skimmer and salt creep could be the culprit... I do a 5 gal change every week. I add the topoff to the overflow and let it flow directly into the filter and I take the water to check from the front of the tank. I know that as I lose water and add clean, the salinity drops so I have been topping off with salt water close to what is in the tank. I just checked the RM and the HM, RM read 1.024 and my old HM read 1.0245. I even added some 1.024 topoff water today, and the salinity hasnt changed.