Unchanging salinity

[MikeyZO]

Hi everyone, I'm new to Manhattanreefs, so 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?

 

[Killerdrgn]

how big is your system? 1 gallon of evaporation from say, a 400 gallon system is nothing, and probably wouldn't change the salinity much. And when you top off you need to test away from the location you top off from

 

[NYreefNoob]

^ agreed, depends on how big the tank is. i have about 55g total and if i lose a gallon doesnt really show a difference

 

[MikeyZO]

Its a 36 gal bowfront with 50 lbs of live rock and a ProClear Pro75 wet/dry filter.

 

[tommy818]

salt dosnt evaporate the fresh top off wont change the salinity

 

[Pinkheine]

salt dosnt evaporate the fresh top off wont change the salinity

That was always the impression I had. But when there is a build up of salt, on the lid or things... don't knock it back in but clean it up. Whatever water the skimmer takes out should be replaced with salt water though. Testing salt regularly is still important regardless, but adding top off water should not lessen the level of salt that is present.

 

[MikeyZO]

I agree that topping off to the original level shouldnt change the salinity, but in my case it does. Which either means I'm having a loss of salt someplace, or I have a leak. Now I've checked the entire system very thoroughly and there is no leak that I can detect. So maybe it is a combination of protien skimmer and salt creep?

 

[KathyC]

I agree that topping off to the original level shouldnt change the salinity, but in my case it does.

What does it change it to?

Would be helpful for us to know how many gallons of water your sump holds
I would imagine you wouldn't have a swing of more that .01, even if you lost a couple of gallons to evaporation.
Do you have an ATO yet?

 

[Killerdrgn]

Are you testing the water right after you top off or do you wait a couple of hours?
If you test it right away, the lighter fresh water will technically float for a little while before totally mixing in. If you can kind of imagine an Iced tea mix that is mixed a little heavier than normal, and then you add some more water to the top. The top water will be lighter and more liquidy than the darker bottom. And then after a little while it'll totally mix. same thing happens in salt water.

 

[bad coffee]

Try this.

Draw a picture of the scale you see in your refratometer. Check your water, and mark EXACTLY where it is on the scale you've drawn. if the line is barely over 1.024, mark it there, not on the 1.024 line.

Before you top off again, check the salinity again. Make the mark on your drawing. is there a slight change? I bet there is, but probably not a full point.

I'll admit I just 'ballpark' my salinity. Close enough is good enough for me.

My top-off is what saved my reef more than once. Get one set up!

B