Why is my salinity dropping

[geddavis]

So I recently set up a Red Sea reefer and just put fish in it. Long story short I had some salinity issues but sorted them out and got everything just right. However slowly over the past few weeks my salinity has been dropping. At first a thought it was a leak and my ato was topping it off. When I looked for a leak I found no salt creep or drips. Any idea what could be the cause.
Here is my apex graph

 

[TheHarold]

I would question the apex’s reading firstly. The salinity probes are notoriously unreliable. Check your salinity using another instrument before panicking or jumping to any conclusions. I use me apex’s probe as a reference only, to show trends.

 

[ca1ore]

First thing is to independently confirm that the apex salinity measurement is accurate (often it’s not). Ideally using a calibrated refractometer. If it is accurate then your system is ‘leaking’ salt somewhere. In the skimmate perhaps?

 

[saltyfilmfolks]

All the above.

 

[P-Dub]

I second all the above recommendations. Solid advice.

 

[DesertReefT4r]

Salinity probes are known to act funny. Double check with a refractometer. When was the last time you calibrated the probe? Are your using top off water faster? A skimmer will remove saltwater and can lower SG over time if not kept in check.

 

[geddavis]

I will recalibrate my probe and check the salinity in my skimate to see if it adds up.

 

[McPikie]

Do you not have a refractometer you could check with yourself?

 

[TriggerFinger]

Salinity probes are known to act funny. Double check with a refractometer. When was the last time you calibrated the probe? Are your using top off water faster? A skimmer will remove saltwater and can lower SG over time if not kept in check.

What’s done to keep this in check if your skimmer is removing saltwater? Common sense tells me it’s supposed to do that?? Not being smart, New reefer here with genuine question.

I added a skimmer almost 2 weeks ago and I’ve been adding saltwater as top off bc my salinity is lower instead of higher. Up until your comment I was perplexed bc I have quite a bit of evap in my tank.

 

[Jcat2k]

I will recalibrate my probe and check the salinity in my skimate to see if it adds up.

Really the takeaway advice is to NOT rely on 1 tool to test - regardless of the accuracy of the probe, verify with a different tool. A refractometer is less than 25.00 on Amazon.

 

[afuel]

I have my apex salinity probe calibrated at 35 ppt and its accurate at that point. But if there is a slight decrease or increase in salinity it overstates the change if that makes sense. I have over 200 gallons and 1-2 gallons of extra fresh water has my probe saying I’m at less than 32ppt which shouldn’t be the case and I check it against my refractometer and it barely shows any overall change away from 35ppt. Just had that happen last night while doing a water change I tried to multi task and lost 1-2 gallons of salt water on the floor. So I let my ATO take care of the rest and I’ll slowly get it back spot on over the next week but currently my Apex is needlessly in alarm showing 31.9

 

[McPikie]

Is your prob next to the ATU drop in point?

 

[YES]

So I recently set up a Red Sea reefer and just put fish in it. Long story short I had some salinity issues but sorted them out and got everything just right. However slowly over the past few weeks my salinity has been dropping. At first a thought it was a leak and my ato was topping it off. When I looked for a leak I found no salt creep or drips. Any idea what could be the cause.
Here is my apex graph

When was the last time you calibrated the prob they do need to be re calibrated every 6 -12 months

 

[phlibbyreefer]

mine will lower due to skimmer collection. some days its a bit too wet and too much saltwater is replaced with fresh ato.

 

[Neanderthal]

Have you considered the IceCap salinity/temp digital probe. Well worth the money.

 

[geddavis]

I just got a Red Sea refractometer and wow was all my other gear off mainly the apex. My salinity has not dropped to 1.01 but rather 1.024. I will recalibrate my probe and see what happens. Thanks for all the replies.

 

[afuel]

Yeah I don’t get it mine dropped from sitting at 35 ppt for weeks then in less than a 36 hr time period went down to 29 and back up to 35 without me doing a thing refractometer never waivered and the probe is less than 2 months old

 

[geddavis]

Yeah I don’t get it mine dropped from sitting at 35 ppt for weeks then in less than a 36 hr time period went down to 29 and back up to 35 without me doing a thing refractometer never waivered and the probe is less than 2 months old

The apex salinity probe seems to be pretty untrustworthy lukily I have a new cleaner shrimp coming soon.

 

[sotomike]

I had same issue. I have the reef mat 1200 and my salinity dropped. I believe that the side effect of the reef may is that it takes water out along with the salt and therefore lowers my salinity and my ato just hides the issue.