Scheduled Skimmer's Affect on Salinity.

[Biglurr54]

So I have my apex set up to run my skimmer at night for 8 hours. I don’t need to have the skimmer running all the time and would rather save the energy and leave the food in the water column for the corals. I have been tracking my salinity with a PM2 in the return chamber (Same chamber as the ATO). I have also been taking nightly refractometer readings with a perfectly calibrate refract. Refractometer is showing 35ppt. But I have noticed salinity swings on the PM2.


The skimmer is in a chamber before the return. Its an SRO int3000sss. It take a bit of water to run. When the skimmer turns on at midnight, the ato kicks in and dumps a good amount of fresh water in and then continues to kick on about once an hour. Then when the skimmer turns off at 8:00am, the skimmer empties and the water level rises in the sump. The water then evaps all day (Salinity increases) until midnight where it will kick back on when the skimmer comes on.


Im worried about the stability of the salinity in this set up. I am wondering if I should just let it go and that this is just an effect of being able to quantify the changes due to use of precise measurements and graphs vs taking once nightly readings via Refectormeter with human error. My PM2 graphs show drastic changes. At the end of the day, we are talking about a gallon of water in a 220 gallon system so how much drift in salinity can there be?

 

[Randy Holmes-Farley Verified Community Expert]

How large are the observed changes? Can you post the graphs?

The change by adding 1 gallon of fresh water to 220 gallons of salt water is a reduction from, say 35.00 ppt to 34.84 ppt, or a sg change from 1.0264 to 1.0263.

Some controllers allow for different temperature corrections for conductivity, so can inherently be set incorrectly as well. That produces the appearance of a salinity swing over 24 h, even if there may not be one.

 

[Larry L]

At 35 parts per thousand, the amount of "stuff" in your water is:

(35 gallons of stuff / 1000 gallons of water) * 220 gallons of water = 7.7 gallons of stuff

So with that same 7.7 gallons of stuff in 221 gallons of water, you'd have 7.7 / 221 = 0.0348 which is 34.8ppt

would rather save the energy and leave the food in the water column for the corals

I'm curious about this, I've read in a couple other places about people having the same idea - have you noticed any difference or do you know anyone who has noticed a difference?