# Seachem Purigen & Activated Carbon



## _Maq_ (1 Sep 2022)

In my native community (Czech), using activated carbon or Seachem Purigen is often bitterly disputed. Most of my compatriots do not care about anything like 'organic pollution', they are focused solely on inorganic nitrogen species.
Here, organic pollution seems to be taken more seriously. Yet the main way to combat it are apparently regular massive water changes. (I don't know anything about the price of water in yours, yet in current state of rising prices this might be a matter of serious consideration.)
Not much I've read here about activated carbon, and namely Purigen. I'd like to know whether you use them to reduce organics, and what do you think of their effects. Any comment will be welcome.


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## dw1305 (1 Sep 2022)

Hi all,


_Maq_ said:


> Not much I've read here about activated carbon, and namely Purigen. I'd like to know whether you use them to reduce organics, and what do you think of their effects. Any comment will be welcome.


We have a few Purigen threads, at least one of these suggests that it filters out <"organic molecules on size">.

Seachem are famously opaque about what <"their products actually are">, but I'd guess that this is about right <"7.4.6. Purigen">.

We get through a lot of activated charcoal at work, we use it to decolourise the soil samples before spectrophotometry, so it does work, but it is quite an expensive option.  The most cost effective way to remove organic compounds, from relatively clean water, is via a <"slow sand filter">, but you need somewhere to put the filter.

Personally I actually <"like a few tannins">, so I don't use any chemical, or mechanical, <"fine filtration"> methods.

I've used the <"BOD concept for a long time">, so I don't regard all organic molecules in the same way, have a look at <"Wood for tanks?">. All I'm really <"interested in"> is a compounds capacity <"to remove oxygen"> from the water column.

There is a useful discussion in <"So what is organic wastes?">

cheers Darrel


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## _Maq_ (1 Sep 2022)

I'm sorry, too late I've found other threads already dedicated to Purigen and AC. Interesting reading.
And I understand and agree that hard-to-decompose organic substances work in different way. Humic substances, for example, are natural chelators, which might be useful. I wonder if tannins are able to form complexes with metal ions as well?


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## dw1305 (1 Sep 2022)

Hi all, 


_Maq_ said:


> I'm sorry, too late I've found other threads already dedicated to Purigen and AC. Interesting reading.


I don't think new threads are ever a bad idea, even if it is something that exists in the UKAPS forum archive. We have new members all the time, who may have  a new perspective to offer. 

cheers Darrel


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## _Maq_ (1 Sep 2022)

dw1305 said:


> I'd guess that this is about right <"7.4.6. Purigen">.


I don't like it.
I'm not the one to expect that AC or Purigen would lower inorganic nitrogen content significantly. However, the author himself permits that Purigen and AC do remove organic dyes. Do they have 'eyes' to see which organic compound has a colour? Of course not. So it suggests that they remove non-polar organic compounds no matter if they colour the water or not.
I think the author's view had been biased from the beginning. _He has not got a faintest idea what nitrogen containing organic compounds exist?_ Well, then he should learn first!


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## dw1305 (1 Sep 2022)

Hi all,


_Maq_ said:


> Do they have 'eyes' to see which organic compound has a colour? Of course not. So it suggests that they remove non-polar organic compounds no matter if they colour the water or not.


I think you are right, it is just more obvious <"with a coloured compound"> when you use Purigen. With activated charcoal you can't see the change in colour of the charcoal, but you can see the change in colour of the filtered liquid.


_Maq_ said:


> I'm not the one to expect that AC or Purigen would lower inorganic nitrogen content significantly.


It won't, but I think the problem is partially back with Seachem <"and their advertising strategy">. We talk, and understand about "ions", the relative sizes of molecules, organic and inorganic carbon etc, but for a lot of aquarists those differentiations  aren't that obvious and they can be bamboozled <"by clever wording">.


_Maq_ said:


> He has not got a faintest idea what nitrogen containing organic compounds exist?


He says:


> ......... If they are talking about the soluble proteins and amino acids produced by uneaten food and by feces, there is no way to selectively remove these “waste” compounds and then prevent those compounds from breaking down into ammonia. It can’t be done.........



cheers Darrel


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## xZaiox (1 Sep 2022)

I would imagine Purigen's utility will likely come in adsorbing miniscule organic compounds that are too small for the filter to otherwise catch.


dw1305 said:


> <"7.4.6. Purigen">.


Although this link claims that it left nitrate levels unaffected, the author also states that no water changes were done. Purigen is typically removed after it exhausts itself (indicated by a dark colour), at which point it is regenerated with bleach. Although I do agree that the compounds it attracts are likely being processed by bacteria on the purigen media itself, the media very obviously attracts organic compounds because it drastically changes colour from white to black. Even if these compounds are being broken down on the Purigen itself, they aren't floating around the tank where algae may have an opportunity to take advantage of them instead.

Realistically, I have no clue how much of an impact it actually has on dissolved organics, and whether or not this translates into actual benefits in an aquarium. I used to always run Purigen, but as of right now, I have taken mine out due to speculation that it may adsorb the chelating agents in micro fertilisers. I'm currently having plant issues, and I plan to add Purigen back once I can figure out how to correct the plant health.


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## dw1305 (1 Sep 2022)

Hi all,


xZaiox said:


> I used to always run Purigen, but as of right now, I have taken mine out due to speculation that it may adsorb the chelating agents in micro fertilisers


I'm pretty sure <"it will">.







xZaiox said:


> Purigen is typically removed after it exhausts itself (indicated by a dark colour), at which point it is regenerated with bleach. Although I do agree that the compounds it attracts are likely being processed by bacteria on the purigen media itself, the media very obviously attracts organic compounds because it drastically changes colour from white to black. Even if these compounds are being broken down on the Purigen itself, they aren't floating around the tank where algae may have an opportunity to take advantage of them instead.


Yes, it is going to take out all compounds of a suitable size. Personally I want some humic and tannic compounds <"All the leaves are brown… — Seriously Fish">, so it would be self defeating.

For people who like "gin clear" water I can see it may offer some advantages.

cheers Darrel


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## Wookii (1 Sep 2022)

dw1305 said:


> Personally I want some humic and tannic compounds <"All the leaves are brown… — Seriously Fish">, so it would be self defeating.



Me too - in fact I go to some length to manually add them, making carbon or Purigen redundant in my case also.


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## _Maq_ (1 Sep 2022)

xZaiox said:


> Purigen's utility will likely come in adsorbing miniscule organic compounds that are too small for the filter to otherwise catch.


I think it adsorbs _dissolved_ organic compounds.


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## _Maq_ (7 Sep 2022)

xZaiox said:


> it may adsorb the chelating agents in micro fertilisers


I've been studying this question a bit some time ago. As we know, water processing plants often need to lower the content of various metals, iron and manganese in particular. For this purpose, activated carbon is not applied as its effectiveness is poor in this particular respect. In connection with the fact that in processed waters, most dissolved iron and manganese are bound in natural complexes (humic substances a.o.) it seems to be quite strong argument against fears that activated carbon would bind EDTA or other chelating agents in a significant degree. However, activated carbon provides both substrate (="food", in the form of adsorbed organic compounds) and large colonizing area for heterotrophic bacteria, and these bacteria consume quite a lot of iron. In this sense, yes, AC 'binds' iron, just like all other filtration media designed for bacterial colonization.
The effect of Purigen remains obscure, of course, but we can assume it works in more or less similar way.
Activated carbon is manufactured from organic matter (coal, coconut coir & shells, wood, etc.), and as such, it always contains remains of various biogenic elements. Phosphorus is often mentioned, and trace metals, too. Unless it's acid washed before use, it is likely to leak more metals than it adsorbs.
Well, that's what literature says, the theory.
Yet I'd like *to know more about your experience* with activated carbon and Purigen. Organic pollutants other than those difficult-to-degrade humic compounds likely play a very significant role in our tanks. Mostly negative one, I believe. Can you see any visible benefits in using each of them, and any differences between them?


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## xZaiox (7 Sep 2022)

@_Maq_ - I found your above post very interesting, I'm not at all familiar with processing plant procedures.


_Maq_ said:


> Yet I'd like *to know more about your experience* with activated carbon and Purigen.


I'm still currently experiencing paleness and whitening of certain plants with Purigen taken out of my filter, so I definitely can't say for sure either way. I plan to add it back to my filter if/when I can correct whatever issue is in my tank, so I can let you know if I see any changes. I'm honestly doubtful that it has any significant impact, although I will add, that DTPA Iron and EDDHA Iron will generally stain the water a different colour when enough is added, and Purigen removes this discolouration, so I'm logically assuming that it is removing the chelated iron, although I can't say for sure.


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## _Maq_ (7 Sep 2022)

xZaiox said:


> DTPA Iron and EDDHA Iron will generally stain the water a different colour when enough is added, and Purigen removes this discolouration


Here, I'm at the end of my brains. Theory says AC (and probably Purigen, too) adsorb *non-polar* compounds. Chelating agents create complex salts. Par example Fe-EDTA is in fact Na-Fe-EDTA where the bond between sodium and EDTA (conjugate base) is *polar*. In water, it dissolves into sodium cations and EDTA-anions with Fe ion "imprisoned" within. If I'm correct, then this is not a non-polar specie, and as such it should not be very attractive for AC or Purigen to adsorb.
It's just my speculation, and I'd really like *if someone could explain*.


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## _Maq_ (18 Sep 2022)

Well, I've started this thread and said nothing about my experience with AC and Purigen.
I find them useful. Maybe it's my obsession but I consider dissolved easily-degradable organic compounds the greatest danger for plants, and also an algae trigger. AC does not change the game instantly but usually after a week or so I can see remarkable improvement. Especially if combined with water changes. (I'm employing no filters so I'm using a bag with AC hanging on the side directly in the tank.)
I can't tell any difference between Purigen and AC made from coal. However, I've experimented with AC made from coconut and compared it with the other one. Generally, AC made from coconut possesses smaller pores and is recommended primarily for gas filtration. Gas molecules are usually smaller. And yes, I've detected that AC from coconut was markedly ineffective in capturing some organic dyes like Acriflavin, tea tannins and peat extract (all huge molecules). AC of coal performed better.
The big advantage of Purigen is that it can be easily regenerated. I don't use bleach but 1 per cent hydrogen peroxide with good results. If Purigen is really deep brown, it may take several days and I have to renew the solution several times. Yet the advantage is that H2O2 leaves no traces of chlorine or ammonia.
Also, if used in water of low conductivity, AC can raise pH and TDS-EC. To avoid that, acid washed AC is preferable, but also more expensive. I prepare my own acid washed AC by washing it in 10 per cent hydrochloric acid. It's laborious and it smells (hydrogen sulfide is generated). After that, it requires washing it in RO water many times to get rid of all salts and residues of the acid. I do not recommend that, but I'm a bit crazy...

I know from good sources that regeneration of AC is an advanced process which we cannot perform with common tools. High temperature and high pressure are required. Still, I wonder that H2O2 could possibly work somehow? All but very resistant organic compounds oxidize in the presence of hydrogen peroxide. It can clean Purigen, so why not activated carbon? Just a layman's idea, but would be grateful if anyone better informed could explain.


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## jaypeecee (29 Dec 2022)

Hi @_Maq_



_Maq_ said:


> I consider dissolved easily-degradable organic compounds the greatest danger for plants, and also an algae trigger.



I couldn't agree more!

JPC


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## PARAGUAY (29 Dec 2022)

One of the best aquarium shops used to drop squares of Polyfilter in their tanks to prove it's effectiveness,it worked just as well in the filter or on the substrate


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## AlecF (30 Dec 2022)

Aren't "dissolved organic compounds" in effect mulm, which some people encourage, and which in the kind of ecosystem I'm used to thinking of as good for plants? What else is the bottom of a river bed? Newbie query.


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## jaypeecee (30 Dec 2022)

AlecF said:


> Aren't "dissolved organic compounds" in effect mulm?


Hi @AlecF 

Mulm is _decomposed_ organic matter and often settles on the substrate. An example would be fish waste. It is visible. By definition, dissolved organic compounds are _dissolved_ in the aquarium water and are not visible. Examples would be simple sugars, proteins and organic phosphates.

JPC


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## jaypeecee (30 Dec 2022)

PARAGUAY said:


> One of the best aquarium shops used to drop squares of Polyfilter in their tanks to prove it's effectiveness,it worked just as well in the filter or on the substrate


Hi @PARAGUAY 

I was under the impression that Arcadia PolyFilter only removed inorganic elements. But, according to their blurb, it also "Absorbs proteins and amino acids".

JPC


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## AlecF (31 Dec 2022)

Thanks @jaypeecee. What else would cause dissolved organic compounds? @_Maq_ do you simply add a bag of Purigen inside your aquarium, given you don't use any filter?


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## _Maq_ (31 Dec 2022)

AlecF said:


> @_Maq_ do you simply add a bag of Purigen inside your aquarium, given you don't use any filter?


Yes. No issues, except it's not exactly beautiful.


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## PARAGUAY (31 Dec 2022)

jaypeecee said:


> Hi @PARAGUAY
> 
> I was under the impression that Arcadia PolyFilter only removed inorganic elements. But, according to their blurb, it also "Absorbs proteins and amino acids".
> 
> JPC


Hi well they would show you tanks were the Polyfilter changed colour and was actively taking out pollutants heavy metals etc think what impressed was the fact it took out ammonia nitrite and " polished "the water. Think at the time the price put me off. Whether it's needed or beneficial to a healthy we'll planted aquarium is debateable


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## fredi (31 Dec 2022)

Personally I use carbon when starting a new tank (just in case), and after medication. Imho continuous use is a band aid, never used purigen etc, never felt the need


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## jaypeecee (31 Dec 2022)

AlecF said:


> What else would cause dissolved organic compounds?


Hi @AlecF 

Aquatic plants release a cocktail of organic compounds into the water. And algae can feed on these compounds. Some people also add Catappa leaves, etc., which release tannins, giving the water a brown tint. Fish food often contains organic compounds. The list goes on...

JPC


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## AlecF (1 Jan 2023)

Ah yes, the debate between lager and dark beer. The pristine tank versus the tinted bit of a river.  Thanks for explaining.


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