Seachem Clarity: what it ISN'T, and a possible mechanism of action

[taricha]

This is about Seachem Clarity and its use for water clarifying. I don't know exactly what it is, but I know a common guess that it is not, and I thought I'd post a little about how it seems to behave.

The manufacturer page describes it as "...the ultimate clarifier for both fresh and saltwater. It employs an advanced polymeric flocculating agent that is both reef and plant safe. ... Clarity™ will clear all types of clouding."

The SDS sheet (attached) says
"* Proprietary aqueous solution of iron salt and other ingredients, including polymeric flocculating agent, which are non - hazardous or less than 1% in concentration (or 0.1% for carcinogens, reproductive toxins, or respiratory sensitizers). Specific chemical identity of salt, polymers and other ingredients and exact percentage concentration withheld as proprietary trade secrets."

First, there is a widely used polymer flocculant in drinking water - polyDADMAC (wiki). It has been suggested in a few places (including by me... oops) that maybe aquarium clarifiers like Clarity use this polymer. I don't know about others, but Clarity looks like it's NOT a cationic polymer.
PolyDADMAC is a polyquat or cationic polymer with a high charge density. I have used several different methods that detect or quantify polyquats / cationic polymers. Clarity does not behave like it contains any cationic polymer at all in response to any of these methods: SDS, bromophenol blue, or toluidine blue o titration. The last method is used in fairly standard test kits (Lamotte) for polyquat measurement, and has been used on polyDADMAC specifically.

Here's what I did find out about how Clarity behaves. It is very acidic in the bottle (below pH of 3) , and as soon as you bring the pH up even slightly (above 4), it forms solids and falls out of solution. This would happen in fresh or saltwater aquaria.

Here's what happens with a dilute solution of Clarity (3%) in distilled water as you bring the pH up with dropwise addition of 1M NaOH...

adding the clarity drops the pH below 3. Stirring alone for 10 minutes does nothing - the solution remains light brown (1st pic from left). Adding NaOH drops does little to raise the pH initially, but creates darker colored solids that settle out of the still yellow liquid when the stirring is turned off (pics 2 and 3). Eventually the pH starts to rise quickly with each drop and more NaOH no longer precipitates solids, and the remaining water after settling is totally clear (pics 4 and 5).

This worked the same when adding saturated sodium bicarbonate solution instead of NaOH, see below...

And it worked the same in tank water. I took aquarium water, lowered the pH to ~2.5 with HCl before adding Clarity.
It was totally stable without precipitate until the pH was raised back up with NaOH. The precipitation occurred and was finished before the pH got even to 5.

Since the pH will obviously go above ~4 with any addition to fresh or saltwater aquaria, it seems this mechanism will always be triggered.

This also means that the binding mechanism may not involve being cationic (+) and thus would not be expected to bind to negative surfaces in aquaria. The solids seem loose, fluffy and seachem says they need to be filtered.

"Q: I added the correct amount of Clarity™ to my tank and the cloudiness got much worse. What is happening?

A: Clarity™ is a flocculant, meaning it bonds to small particles, making them much larger and easier to filter from the water. This will make the cloudiness worse for a short time until the large particles are removed from the water. Mechanical filtration is the only way to remove them, and if you don't have adequate mechanical filtration it will probably never clear...."

If your water clarifier product is extremely low pH and precipitates well before the pH reaches aquarium levels, then it might be using a similar mechanism / chemical.

(edit: I'm not a polymer chemist or chemist of any sort, so people with actual expertise may have a different interpretation.)

 

[Dan_P]

This is about Seachem Clarity and its use for water clarifying. I don't know exactly what it is, but I know a common guess that it is not, and I thought I'd post a little about how it seems to behave.

The manufacturer page describes it as "...the ultimate clarifier for both fresh and saltwater. It employs an advanced polymeric flocculating agent that is both reef and plant safe. ... Clarity™ will clear all types of clouding."

The SDS sheet (attached) says
"* Proprietary aqueous solution of iron salt and other ingredients, including polymeric flocculating agent, which are non - hazardous or less than 1% in concentration (or 0.1% for carcinogens, reproductive toxins, or respiratory sensitizers). Specific chemical identity of salt, polymers and other ingredients and exact percentage concentration withheld as proprietary trade secrets."

First, there is a widely used polymer flocculant in drinking water - polyDADMAC (wiki). It has been suggested in a few places (including by me... oops) that maybe aquarium clarifiers like Clarity use this polymer. I don't know about others, but Clarity looks like it's NOT a cationic polymer.
PolyDADMAC is a polyquat or cationic polymer with a high charge density. I have used several different methods that detect or quantify polyquats / cationic polymers. Clarity does not behave like it contains any cationic polymer at all in response to any of these methods: SDS, bromophenol blue, or toluidine blue o titration. The last method is used in fairly standard test kits (Lamotte) for polyquat measurement, and has been used on polyDADMAC specifically.

Here's what I did find out about how Clarity behaves. It is very acidic in the bottle (below pH of 3) , and as soon as you bring the pH up even slightly (above 4), it forms solids and falls out of solution. This would happen in fresh or saltwater aquaria.

Here's what happens with a dilute solution of Clarity (3%) in distilled water as you bring the pH up with dropwise addition of 1M NaOH...
View attachment 2992563

adding the clarity drops the pH below 3. Stirring alone for 10 minutes does nothing - the solution remains light brown (1st pic from left). Adding NaOH drops does little to raise the pH initially, but creates darker colored solids that settle out of the still yellow liquid when the stirring is turned off (pics 2 and 3). Eventually the pH starts to rise quickly with each drop and more NaOH no longer precipitates solids, and the remaining water after settling is totally clear (pics 4 and 5).

This worked the same when adding saturated sodium bicarbonate solution instead of NaOH, see below...
View attachment 2992594


And it worked the same in tank water. I took aquarium water, lowered the pH to ~2.5 with HCl before adding Clarity.
It was totally stable without precipitate until the pH was raised back up with NaOH. The precipitation occurred and was finished before the pH got even to 5.

View attachment 2992599


Since the pH will obviously go above ~4 with any addition to fresh or saltwater aquaria, it seems this mechanism will always be triggered.

This also means that the binding mechanism may not involve being cationic (+) and thus would not be expected to bind to negative surfaces in aquaria. The solids seem loose, fluffy and seachem says they need to be filtered.

"Q: I added the correct amount of Clarity™ to my tank and the cloudiness got much worse. What is happening?

A: Clarity™ is a flocculant, meaning it bonds to small particles, making them much larger and easier to filter from the water. This will make the cloudiness worse for a short time until the large particles are removed from the water. Mechanical filtration is the only way to remove them, and if you don't have adequate mechanical filtration it will probably never clear...."

If your water clarifier product is extremely low pH and precipitates well before the pH reaches aquarium levels, then it might be using a similar mechanism / chemical.

(edit: I'm not a polymer chemist or chemist of any sort, so people with actual expertise may have a different interpretation.)

Funny stuff.

Once the precipitate forms, does it dissolve when diluted or is pH the sole factor in controlling solubility?

If you recast your titration data to pH vs volume of base added, does the data look like a normal titration or whacky because the pH drifts with time?

 

[taricha]

Funny stuff.

Once the precipitate forms, does it dissolve when diluted or is pH the sole factor in controlling solubility?

If you recast your titration data to pH vs volume of base added, does the data look like a normal titration or whacky because the pH drifts with time?

Doesn't dissolve with dilution.
I didn't think to check if dropping pH back down re-dissolves the solids.

With Clarity in just distilled water, it would pretty much look like a normal titration. Clarity in saltwater might look weirder.

 

[Sean Clark]

Obviously, it's magic...

 

[taricha]

Once the precipitate forms, does it dissolve when diluted or is pH the sole factor in controlling solubility?

If you recast your titration data to pH vs volume of base added, does the data look like a normal titration or whacky because the pH drifts with time?

Doesn't dissolve with dilution.
I didn't think to check if dropping pH back down re-dissolves the solids.

Here's the solids resuspended in distilled water, tap water, and distilled +HCl.
Not soluble just with dilution, but soluble with acid.

Also stirring a small dusting of the solids in 0.5L distilled water, letting them settle, changing another 0.5L of distilled water and stirring for another half hour seems not to dissolve it.

With Clarity in just distilled water, it would pretty much look like a normal titration.

here's a titration done with auto-stirring.
100mL water with 3mL Clarity.
0.10mL of 1M NaOH added every 30 sec
then coming down, 0.10mL of 1M HCl added every 30 sec.
(so the time axis is the Base/Acid added axis, 0.2mL of 1M every minute)

Coming down in pH took way more acid and way longer to re-dissolve all the solids. It was probably stirred at pH of 2.0 for ~30 min before all solids finally re-dissolved.

 

[Dan_P]

Here's the solids resuspended in distilled water, tap water, and distilled +HCl.
Not soluble just with dilution, but soluble with acid.
View attachment 2993771
Also stirring a small dusting of the solids in 0.5L distilled water, letting them settle, changing another 0.5L of distilled water and stirring for another half hour seems not to dissolve it.




here's a titration done with auto-stirring.
100mL water with 3mL Clarity.
0.10mL of 1M NaOH added every 30 sec
then coming down, 0.10mL of 1M HCl added every 30 sec.
(so the time axis is the Base/Acid added axis, 0.2mL of 1M every minute)
View attachment 2993775

Coming down in pH took way more acid and way longer to re-dissolve all the solids. It was probably stirred at pH of 2.0 for ~30 min before all solids finally re-dissolved.

Thanks for the update.

Is the yellow-orange solid in the centrifuge tube likely the substance that helps form flocs?

 

[Randy Holmes-Farley]

Maybe I'm missing something because I read it pretty quickly, but the solids would seem to result in all of these ways just from the iron. Color, pH dependence of solubility, etc.

 

[taricha]

the solids would seem to result in all of these ways just from the iron. Color, pH dependence of solubility, etc.

I wondered the same thing - if there was actually polymer falling out of solution or if it was just the brown Iron.
This was a crude thing I did to try to distinguish.

I took some undiluted product in two tubes, and added NaOH to the left, then centrifuged to settle the solids.


Then I dried 3 drops of each on a slide placed on a coffee warmer...

The straight product leaves the brown clear shiny slick on the right like other aquarium polymers. The clear liquid from the treated product dried to the white crust of crystals on the left (I probably way overshot the NaOH.)
After cooling, the white crust is easy to break and push apart with my thumb. The dried brown slick is stronger and doesn't budge, feels plastic-y. (can still wash it off with soap and water though.)

Since it isn't a cationic polymer, this all I could think of to see if the polymer was likely still in the liquid or if it was with the solids that fall out of solution.

 

[taricha]

Is the yellow-orange solid in the centrifuge tube likely the substance that helps form flocs?

That's my guess - since the falling out of solution is unavoidable at anything near aquarium pH, I'm guessing whatever it grabs as it falls out is what it clarifies.

Oh, the solids fall down quickly in freshwater, but are more neutrally buoyant and take much linger to settle in saltwater. So more will be caught by filtration.

 

[Randy Holmes-Farley]

I can certainly believe that the iron precipitation also takes down a polymer with it. Many anionic polymers will be pretty good at binding to iron oxide/hydroxide/free iron.

https://pubs.acs.org/doi/abs/10.1021/la971126l