Salinity

[Rainblood]

My zoas were pouting a little bit yesterday so I did a water change and checked the salinity of the tank. What the heck...it was showing 1.023.
I used both a refractometer & a hand held one.

How does that happen? If its just top offs and water changes, is it the skimmer thats taking out salt? I can't think of anything else

 

[ZapataInc]

My zoas were pouting a little bit yesterday so I did a water change and checked the salinity of the tank. What the heck...it was showing 1.023.
I used both a refractometer & a hand held one.

How does that happen? If its just top offs and water changes, is it the skimmer thats taking out salt? I can't think of anything else

That and any salt creep.

 

[Rainblood]

what is salt creep

 

[dball711]

Is the temp constant when taking a reading? Could be the refractometer is out of calibration or maybe not a good one? Cant ee how a skimmer would take salt out.

 

[dball711]

Salt creep is when water evaporates and salt builds up as a crusty form around the top. Doube this would affect the salinity much but might have an effect.

 

[ZapataInc]

This is an example of salt creep



But yeah I doubt either skimming or salt creep would bring your numbers down that much. How big is the system?

 

[Rainblood]

Is the temp constant when taking a reading? Could be the refractometer is out of calibration or maybe not a good one? Cant ee how a skimmer would take salt out.

yes i calibrated it with rodi water but its an el cheapo refractometer. i double checked with a hydrometer.
its not salt creep...my tank is crusty.

i didnt think a skimmer removes salt but i have no idea.

 

[Rainblood]

Its a Nuvo40

 

[Rainblood]

I recently removed a large rock when I re-scaped the tank...do rocks absorb salt?

 

[ichthyoid]

If your normal salinity is 1.025 and it dropped to 1.023 that’s an ~8% change.

I would be inclined to look at what I’m measuring it with first.

 

[ichthyoid]

I recently removed a large rock when I re-scaped the tank...do rocks absorb salt?

If you removed a large rock and allowed the ATO to make up the difference, that could do it.

 

[Rainblood]

If you removed a large rock and allowed the ATO to make up the difference, that could do it.

I bet that was probably it

 

[Steve Burton]

I wouldn't suggest calibrating at zero using Rodi water. I calibrate mine with 35 PPT calibration fluid

 

[ActiveAngel]

If you removed a large rock and allowed the ATO to make up the difference, that could do it.

This is definitely it.

As for Salt creep, yes it’s a factor. But in a 40g, that’s a crap-Ton of salt... you almost certainly would have noticed.

... but @ichthyoid is on point. If you removed a rock, and didn’t compensate by adding salt when you did this, then your salinity is absolutely going to drop.

 

[ZapataInc]

So why wouldn't a skimmer attribute to taking salt out of the system. It does collect liquid which I assume is more than just waste. It may not be the cause of the drop in salinity but I would think that some of that liquid is salt water. Who wants to taste their skimmate for scientific purposes?

 

[Steve Burton]

Taking saltwater out doesn't change the salinity ( unless you replace it with fresh water)

 

[ZapataInc]

Taking saltwater out doesn't change the salinity ( unless you replace it with fresh water)

But if you have an ATO then that replenishes what was taken out by evaporation and what goes into the skimmer cup.

 

[ichthyoid]

While a skimmer may remove some salts in the process of skimming, calcium in particular, it’s not enough to throw off the salinity by the 8% you saw.

Most of us dump a cup of skimmate maybe a couple times a week. That’s a small fraction of the tank volume.

Larger systems have skimmate lockers, often of about a gallon, and dump them maybe once a month or so.

On average, less than 1% of the tank’s volume, I’d say.

 

[ZapataInc]

While a skimmer may remove some salts in the process of skimming, calcium in particular, it’s not enough to throw off the salinity by the 8% you saw.

Most of us dump a cup of skimmate maybe a couple times a week. That’s a small fraction of the tank volume.

Larger systems have skimmate lockers, often of about a gallon, and dump them maybe once a month or so.

On average, less than 1% of the tank’s volume, I’d say.

Yeah I agree that it wasn't the cause but it can attribute to salinity loss. I think of people who run a system without water changes... They would probably have to periodically add some saltwater to their system.

 

[Cook]

So why wouldn't a skimmer attribute to taking salt out of the system. It does collect liquid which I assume is more than just waste. It may not be the cause of the drop in salinity but I would think that some of that liquid is salt water. Who wants to taste their skimmate for scientific purposes?

Sounds like it was your idea, so go for it and report back. I just emptied the cup on mine this morning unfortunately.