Salinity and Activated Carbon.

[Kevind0905]

Hope everyone is having a good weekend so far. Have a question regarding activated carbon and salinity. Has anyone ever experienced a salinity drop after adding it? I put about ½ cup into my 69 gal yesterday (mesh bag in low flow area of sump). Salinity was 1.0255 (33.8ppt) before adding and 1.0225 (29.9ppt) this AM. I use the Hanna Salinity tester. I calibrated the checker on the 14th and double checked it this am. Its spot on according to the calibration solution.

No change in other parameters. Also, checked all water levels and the ATO. All are normal and working correctly. Any thoughts or experiences are welcome.

Thanks!

 

[Flippers4pups]

I've never heard of a salinity drop with use of GAC. I suspect a testing error.

 

[Kevind0905]

My initial thoughts too. Tested it 3 times then re-calibrated the meter. Tested the calibration solution , one of my other tanks, a fresh batch of salt water I made earlier in the week and the tank in question. Still got the low measure. I’m stumped. No other parameters are off. It’s weird.

 

[Reesj]

Definitely not carbon. Dood did you even think what you typed? Your carbon would have to absorb way over it's own weight to get that much of of a salinity drop.

 

[xxkenny90xx]

Ya, DOOD you even think what you typed, lol

 

[Kevind0905]

I hear you; any other explanations? I've searched all over the web. Can't find any other probable causes. I wouldn't even post if it weren't for the fact the drop happened overnight. My first thought was the ATO ran away but I'm using the Tunze and it checks out. Tank is 6 weeks old; going through the ugly statge but even that's not what I would call bad. Minimal bio load. 2 small clowns, 7 corals; 2 Euphyllia (4" and 3"), 5-polup Zoa, candy cane (about 3"), a three polup favia, a plate coral (2") and scoly (3"). The candy cane is retracted a bit today but seems to be responding to slow return of salinity (dripping a concentrate right now). I suppose some things will never be explained but wanted to ask. There is a ton of knowledge here! Thanks again!

 

[Reef.]

Some people have been told the Hanna checker is not designed to test tank water when they have complained it is not accurate, apparently it’s only accurate when testing freshly mixed water. The tank water is said to throw off the accuracy because of the other contaminates tank water contains, so my guess is, your result is a mix of that and also the carbon removing some of those contaminates, which in turn alters the results you are getting.
I suspect the salinity haven’t changed, just the result your Hanna is able to read.

 

[xxkenny90xx]

Sorry i was being sarcastic since he complained about what you wrote but spelt "did" wrong. As far as the salinity drop that is very weird. Did your skimmer by chance go crazy and remove a bunch of saltwater which your ato then replaced with fresh lowering salinity?

 

[Kevind0905]

Some people have been told the Hanna checker is not designed to test tank water when they have complained it is not accurate, apparently it’s only accurate when testing freshly mixed water. The tank water is said to throw off the accuracy because of the other contaminates tank water contains, so my guess is, your result is a mix of that and also the carbon removing some of those contaminates, which in turn alters the results you are getting.
I suspect the salinity haven’t changed, just the result your Hanna is able to read.

Have heard that too; although, I think the advice has been confused. The additional materials in the tank affect density not conductivity. Therefore, refractometers suffer measurement drift and not conductivity checkers. Check out this link (https://aquanerd.com/2018/12/how-to-use-hanna-instruments-salinity-tester.html).

 

[Kevind0905]

Sorry i was being sarcastic since he complained about what you wrote but spelt "did" wrong. As far as the salinity drop that is very weird. Did your skimmer by chance go crazy and remove a bunch of saltwater which your ato then replaced with fresh lowering salinity?

No worries. Skimmer hasn't been skimming. Bio load is too low so all I get is ultra thin skimmate. Really my skimmer is just a glorified aereator at this point.

 

[xxkenny90xx]

Gotcha. Just a side note, when it produces the ultra thin skimmate it is still removing saltwater from the tank which your ato replaces with freshwater. But it doesnt sound like that was your issue so just keep a close eye on your levels

 

[Reef.]

Have heard that too; although, I think the advice has been confused. The additional materials in the tank affect density not conductivity. Therefore, refractometers suffer measurement drift and not conductivity checkers. Check out this link (https://aquanerd.com/2018/12/how-to-use-hanna-instruments-salinity-tester.html).

There is a very detailed thread on here where someone was told the Hanna was not meant to be used for tank salinity checks because the conductivity would be affected, and that was by a supplier of the Hanna checkers, whether that information from the supplier is correct or not I don’t know, but it does sound reasonable that different elements in tank water could affect a conductivity reading.

 

[Kevind0905]

Gotcha. Just a side note, when it produces the ultra thin skimmate it is still removing saltwater from the tank which your ato replaces with freshwater. But it doesnt sound like that was your issue so just keep a close eye on your levels

Will do and thanks. As an aside, this particular skimmer has an overflow that returns water to the tank when/if it overskims (aparently this was Red Sea's answer to a known problem). Also, my ATO volume was not lower than it seemed like it should have been. I'm not measuring its volume per se, but that big a drop so fast seems like it should have dropped the ATO reservoir more than it was when I found the problem. Who knows at this point. One thing for sure, I am going to order a lab grade hydrometer as a back up. Everything I read says conductivity is the best measure of salinity but I think a back-up is a good idea.

Thanks again!

 

[Reef.]

You could always test it, 2 tubs of water, one tank water and one freshly mixed salt water, test each before adding a bag of carbon, then again after adding, see the results.

 

[Randy Holmes-Farley]

There is a very detailed thread on here where someone was told the Hanna was not meant to be used for tank salinity checks because the conductivity would be affected, and that was by a supplier of the Hanna checkers, whether that information from the supplier is correct or not I don’t know, but it does sound reasonable that different elements in tank water could affect a conductivity reading.

It's not correct. Any given conductivity probe may not have the dynamic range to measure salinity that high, but conductivity as a method is PERFECT for measuring salinity. it is how oceanographers do it. It is how the practical salinity scale is defined! The HI 98319 does measure salinity OK, at least according to their published specifications.

Salinity of seawater measured by conductivity cannot ever be impacted either by activated carbon, or any impurity in reef aquariums.

This is not a random opinion. It is an absolute fact.

No pollutants in reef tank water serve to reduce the conductivity (and hence the salinity) in any measurable way.

All ions add to conductivity (salinity), in proportion to their concentration.

With the exception of H+ and OH-, which are very low in seawater and have no significant contribution to seawater conductivity, there are no chemicals that have any substantially bigger contribution to conductivity per ion than the main contributors to conductivity of seawater (sodium, chloride, magnesium, and sulfate).

Thus, for any chemical to raise conductivity to a substantial degree, these chemicals would have to be comparable to these ions in concentration. No such contaminants exist in reef aquariums.

 

[Randy Holmes-Farley]

You could always test it, 2 tubs of water, one tank water and one freshly mixed salt water, test each before adding a bag of carbon, then again after adding, see the results.

That would work, and would be a waste of time.

 

[Randy Holmes-Farley]

FWIW, I discuss the conductivity of individual ions and how that relates to conductivity as a way to measure salinity here:

Using Conductivity to Measure Salinity

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[Cory]

Its experiment time

Cup of tank water compared to in tank water to rule out electrical interference.

Cup of tank water and mix in some activated carbon to see if the dust does any changes.

Mix up some new saltwater and test it. Then add the same amount of tank water into that and see what it says.

Post results

 

[Reef.]

It's not correct. Any given conductivity probe may not have the dynamic range to measure salinity that high, but conductivity as a method is PERFECT for measuring salinity. it is how oceanographers do it. It is how the practical salinity scale is defined! The HI 98319 does measure salinity OK, at least according to their published specifications.

Salinity of seawater measured by conductivity cannot ever be impacted either by activated carbon, or any impurity in reef aquariums.

This is not a random opinion. It is an absolute fact.

No pollutants in reef tank water serve to reduce the conductivity (and hence the salinity) in any measurable way.

All ions add to conductivity (salinity), in proportion to their concentration.

With the exception of H+ and OH-, which are very low in seawater and have no significant contribution to seawater conductivity, there are no chemicals that have any substantially bigger contribution to conductivity per ion than the main contributors to conductivity of seawater (sodium, chloride, magnesium, and sulfate).

Thus, for any chemical to raise conductivity to a substantial degree, these chemicals would have to be comparable to these ions in concentration. No such contaminants exist in reef aquariums.

#RandyHolmes

that was the explanation given by a Hanna supplier when the accuracy was questioned, that they can give incorrect readings when used on tank water because of contamination and are designed to only be used on fresh salt water, maybe the customer was just being fobbed off. I did say I wasn’t sure if the reason given for the inaccuracy was correct.

here is the thread, post #46

Hanna Salinity Tester - first impressions

Mine is way off. Both (fully recalibrated) BRS refractometer and digital controller probe show 1.025 (where its been since day 1), I have used 3 packets of Hanna recalibration liquid and it still reads 1.022. I tried both in the tank and a new mix for watrer changes, same result. It is...

www.reef2reef.com

 

[Randy Holmes-Farley]

Thanks, I posted there to try to correct the faulty BRS info.

After a quick read, the Hanna post earlier in the thread seems fine and does not suggest these issues.