Salinity drop

[Mirugai]

The salinity in my reservoir tank dropped from 1.025 to 1.020 from the very same batch of saltwater mix I made last week. What gives?

I use this reservoir tank with my specpure LiterMeter3 for the auto saltwater change. When I found out that the salinity of my tank dropped I thought the LM3 needs to be recalibrated, but not after I checked the salinity of the reservoir.

My refractometer is calibrated correctly. Anyone got any idea?

[bertoni]

The only way salinity can drop that much is for water to be added.

[Aquarist007]

was there much temperature change in the resevoir from last week to this week

[Oil_Fan]

Also how was your refractometer calibrated? If it's just using RO water, then it maybe still off. I know mine was reading too high by .002 points. One of the LFS here calibrated mine using proper SW calibrating solution. That's how I found out it was off a bit.

Though that still doesn't explain your drop. You sure FW somehow didn't enter into your reservoir?

[bertoni]

Those are good points, too. I was assuming a constant or nearly constant temperature.

[Mirugai]

The only explaination I can think of is when I left the hose that I used to transfer fw into sw reservoir, somehow siphoned the freshwater into the tank. But I had that hose removed a week ago. Could happened the first week I made the batch. I will have to closely monitor this the next time I make a new batch.