Limits to Salinity Stability

[Righteous]

How stable have folks been able to get their salinity? Currently the best I can maintain is about 0.5 - 0.75 ppt variance over the course of several days. I’ve been assuming the fluctuation comes largely from increase/decrease skimmer output, or small variations on sump flow that change the level ATO is reading.

I’m measuring with an Apex salinity probe, along with occasional spot check with refractometer to confirm probe isn’t failing.

Is a conductivity meter like this even consistent on such a level?

And if anyone has been able to maintain more stable salinity, is there noticeable benefit?

 

[Randy Holmes-Farley Verified Community Expert]

Salinity will be as stable as you are able to maintain the exact water volume against evaporation. If you use an ATO, it will turn on and off at various levels that depend on the water level sensing apparatus.

Mine was more stable that yours on a day to day basis, but I’d be surprised if there is any benefit to being more stable than yours against slow changes.

 

[Dkeller_nc]

The stability (or lack thereof) of the Apex conductivity probe has been discussed at length on the forums. It seems that generally people use it as a warning that something's gone catastrophically wrong (like a stuck-on ATO) rather than an absolute measure of the salinity of their tanks. I think that the instability has more to do with the constant-immersion nature of the usage of the probe more than it's a lack of quality in the probe and associated electronics.

 

[Righteous]

I’ve found the apex probe to be relatively consistent and accurate when compared to my refractometer comparison (both are almost always in agreement). I’ve also always assumed it to be generally more consistent than it might be accurate.

 

[Ruben's Reef]

I agree with Randy. I made my gravity ATO and my salinity is always stable at .25 Normally I check my salinity when doing WC to match my DT salinity.

 

[Righteous]

So here’s my apex recently. You can see a fluctuation around 0.6ppt. So this is less stable than others are able to keep things? I realize that it may be nitpicking l, but I like nits

I’ve got a tunze osmolator, btw

 

[Steve1500]

So here’s my apex recently. You can see a fluctuation around 0.6ppt. So this is less stable than others are able to keep things? I realize that it may be nitpicking l, but I like nits

I’ve got a tunze osmolator, btw

Here’s my salinity results. Pretty close to yours and the fluctuation drives me crazy. It slowly increases Over time and I trying to minimize.

 

[rmurken]

Is there a practical effect to swings in salinity of less than 1 ppt? I’ve had a few sudden drops of more than that due to a balky ATO. I basically allowed the salinity to come back up by evaporation, and really couldn’t discern any impact whatsoever.

I have read that sudden increases in salinity can be more problematic, but that’s a harder mistake to make.

 

[DivingTheWorld]

Here’s my salinity results. Pretty close to yours and the fluctuation drives me crazy. It slowly increases Over time and I trying to minimize.

Curious to see if this matches a similar pattern to your temperature chart. At times I will get my salinity probe to be close, but most of the time the numbers are totally useless and the temperature adjustment has never worked from day one. It fluctuates up and down with tank temp.

I know from using a device I trust that I can keep my salinity almost exact (0.1ppt or less) between water changes as long as I'm not taking out too much water (selling frags). I skim very dry so my skimmer doesn't pull out much.