# Seachem Purigen and natural planted tanks



## mysiak (Jan 17, 2018)

So..I jumped on the hype train called "crystal clear water with zero effort and no negative side effects" called Seachem Purigen. I'm sure that everyone heard about it by now, it's probably the most known chemical filtration media. It works by binding dissolved organic compounds to its surface, effectively removing waste before it's metabolized by beneficial bacteria. As a "side" effect it removes also all the tannins which cause brown(ish) water. 

Before purchase, I read a lot of opinions and the most prevailing conclusion was that its use is completely safe in all type of tanks, NPTs including. Who doesn't want a crystal clear water, right? My first bag lasted about 2-3 weeks until it needed regeneration. So I bought another one, so I could alternate between them, this one lasted for a month. This is no where near the claimed 6-12 months of usage, but ok. Water was really crystal clear. However I noticed that many plants started to look bad - old leaves dying very soon, algae growing on them. New growth was healthy, just maybe a little bit slowed down. 

I re-read a couple of chapters of "the book", paying attention to the information about DOC. And it was as I suspected, DOC is quite essential in low tech planted tanks, it doesn't provide only CO2, but helps to make micro ferts available to plants. This corresponds to my observations as well - since I stopped using Purigen, my plants look much better. Water is not airy clear anymore though, but well, we can't have everything 

The situation in high tech tanks is certainly different and I believe that Purigen won't cause any noticeable negative side effects there, but I won't use it anymore in my NPTs.

What's your position? Chemical filtration media (Purigen, carbon, ..) in NPTs - yay or nay?


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## zolteeC (Dec 26, 2017)

mysiak said:


> So..I jumped on the hype train called "crystal clear water with zero effort and no negative side effects" called Seachem Purigen. I'm sure that everyone heard about it by now, it's probably the most known chemical filtration media. It works by binding dissolved organic compounds to its surface, effectively removing waste before it's metabolized by beneficial bacteria. As a "side" effect it removes also all the tannins which cause brown(ish) water.
> 
> Before purchase, I read a lot of opinions and the most prevailing conclusion was that its use is completely safe in all type of tanks, NPTs including. Who doesn't want a crystal clear water, right? My first bag lasted about 2-3 weeks until it needed regeneration. So I bought another one, so I could alternate between them, this one lasted for a month. This is no where near the claimed 6-12 months of usage, but ok. Water was really crystal clear. However I noticed that many plants started to look bad - old leaves dying very soon, algae growing on them. New growth was healthy, just maybe a little bit slowed down.
> 
> ...


Word of warning: I don't have any experience with purigen and this is nothing but guessing below.

I guess it needs a "trained eye" and experience to identify such side effects . Maybe many with low tech tanks will not make a connection between removing too much DOC and sub-optimal growth/a bit more of algae. (I guess when algae hits also many will use non-NPT processes trying to nuke it...)

I am also guessing that negative side effects may depend where the NPT is in its life-cycle. Maybe when tank is new and there is lots of fresh soil in it, the drawback of removing the DOC from the water column may not be such an issue. However, for an "aged" NPT where most of the soils organic matter is gone, and fish food input is critical for healthy tank, removing DOC may be even more counterproductive.

These are really just all guessing and I do not have experience with purigen. However, I was wondering about the same side effect that Mysiak described above, but have not yet convinced myself of doing some testing.

Anyways, those tanks with crystal clear water and purigen really look good.


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## hoppycalif (Apr 7, 2005)

Can anyone answer this? Do plants use specific ions to get the nitrogen, potassium, phosphorous, etc. they need to grow? And, are those the simple inorganic ions? If they do, then organic ions, which include potassium in their make-up (for example) are not bio-available to the plants.


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## mistergreen (Mar 3, 2007)

Plants do uptake ions. I don't think it has to be a specific ion like for Nitrogen, it can be NH4+ or NO3-.


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## hoppycalif (Apr 7, 2005)

mistergreen said:


> Plants do uptake ions. I don't think it has to be a specific ion like for Nitrogen, it can be NH4+ or NO3-.


Yes, but how about an organic ion, with a 10 times larger mass? The reason I asked this is that substances like Purigen and Activated Charcoal adsorb large molecules easily, but not small (inorganic) molecules. If we knew that plants take up primarily or exclusively the inorganic ions, then neither Purigen nor Activated Charcoal can cause problems by removing the nutrients the plants need. For an example: do either of those media remove gluraraldehyde?


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## mistergreen (Mar 3, 2007)

Glut looks big enough for AC to absorb.
plants can uptake chelated micros. Those are organic molecules.


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## mysiak (Jan 17, 2018)

I am just checking the usual deficiency symptoms charts and it seems that I was experiencing lack of multiple mobile nutrients, most probably nitrogen, phosphorus, potassium and magnesium as plants were showing combined symptoms. Lack of nitrogen and phosphorus could be probably explained as Purigen removed DOC containing these molecules. Even though I must say that NO3 was still measurable by testing strips and my tap water is quite hard and contains about 20ppm of NO3. I am not sure how Purigen could impact potassium and manganese. 

Unfortunately I have no test kit for each of these substances, so I can only guess what was happening in the tank.


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## zolteeC (Dec 26, 2017)

hoppycalif said:


> Yes, but how about an organic ion, with a 10 times larger mass? The reason I asked this is that substances like Purigen and Activated Charcoal adsorb large molecules easily, but not small (inorganic) molecules. If we knew that plants take up primarily or exclusively the inorganic ions, then neither Purigen nor Activated Charcoal can cause problems by removing the nutrients the plants need. For an example: do either of those media remove gluraraldehyde?


hoppycalif, I think mysiak point was partly that DOC in the water column will eventually release CO2 as bacteria / who knows what feed on it. With low tech tanks, where we do not dose CO2 gas, the C from this process _may_ be contributing to healthy growth of plants. _Maybe_ getting rid of DOC very efficiently will indirectly have a side effect of having lower amounts of C available for plants. If there is not "enough" C available, plants maybe limited in their capability to "filter" the tank regardless of other nutrient availability.

Maybe dosing "liquid carbo" daily with such non NPT low tech tanks helps (liquid carbo also inhibits algae somewhat, thus reduces plant competitors for C).
_
These points are nothing but guessing from me. _I'd like to see more testing of purigen with NPT tanks (is it still NPT if purigen is used?). 
It's really not that easy to test this, even NPTs that were set up the same way show different rate of plant growth depending on their age and many other factors. 
By the way, maximizing the plant growth for me is not the main goal, for me its more important to have a low maintenance tank where both plants and fish/shrimp look healthy.


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## hoppycalif (Apr 7, 2005)

zolteeC said:


> .....
> 
> By the way, maximizing the plant growth for me is not the main goal, for me its more important to have a low maintenance tank where both plants and fish/shrimp look healthy.


My goal is usually the same, unless I am just trying something. I think every year or two the idea that activated carbon removes nutrients comes up again, and I am 99% sure it doesn't. Purigen isn't something I know a lot about, but I'm guessing it gets the same comments. And, I really enjoy knowing real facts, not just things that get repeated over and over without any verification.

My tank is now a BBA farm, because I missed the fact that the built-in filter pump had jammed up, so my CO2, which I run through that pump, was not getting into the tank water. When I noticed it, probably a week late, and fixed it, the BBA just laughed at me[smilie=b:


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## mysiak (Jan 17, 2018)

I did not say that Purigen or activated carbon remove micro or macro nutrients directly. I don't think that this is happening. But I believe that almost complete removal of DOC can have a detrimental effect on plants. Please correct me if I'm wrong, but DOC is a precursor for at least Nitrogen and Phosphorus. DOC is broken down/converted by bacteria to more simple molecules, which can be used by plants and as a side effect, CO2 is being released. Book also mentions that DOC is helping to make micro ferts like Iron bio-available to plants.

With high tech tanks, one must dose micro/macro ferts pretty much daily, so such effects probably can't be observed. In a low tech tank, we must rely on natural mechanisms.

Of course I might be wrong and I'm fully open to any discussion, I do not have any direct measurements to back up my assumptions. Just observations from two low tech tanks, which both showed very similar symptoms while using Purigen over the course of few months.

My goal is the same as yours guys - healthy plants with healthy fish.


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## zolteeC (Dec 26, 2017)

mysiak said:


> I did not say that Purigen or activated carbon remove micro or macro nutrients directly. I don't think that this is happening. But I believe that almost complete removal of DOC can have a detrimental effect on plants. Please correct me if I'm wrong, but DOC is a precursor for at least Nitrogen and Phosphorus. DOC is broken down/converted by bacteria to more simple molecules, which can be used by plants and as a side effect, CO2 is being released. Book also mentions that DOC is helping to make micro ferts like Iron bio-available to plants.
> 
> With high tech tanks, one must dose micro/macro ferts pretty much daily, so such effects probably can't be observed. In a low tech tank, we must rely on natural mechanisms.
> 
> ...


You mentioned that plants started to look better in those 2 tanks after you removed purigen.
Did you change anything else? How much time did you need to notice the difference?

By the way, there should be tons of P in the soil even if there is almost none in the water column. 
I think the achilles' heel of these low tech tanks is the CO2 / bicarbonate availability for plants. I have no clue how much water column DOC decomposition contributes to CO2 level, would be nice to know. I guess one way to look at it how much "stuff" we phisically remove when purigen is cleaned. May not be too much in volume. For example, if you have a large biofilter, until the filter is not cleaned, the "stuff" in it has a chance to decompose and release CO2 as oxygenated water flows through it. When the filter is cleaned, its only then when that material gets out of the tank and gets lost as a potential CO2 source.
Because purigen needs frequent regeneration, maybe the filter also gets cleaned more frequently, so a "double hit" is taken.

Now we are really not on NPT territory . NPTs do work fine without all this hocus-pocus, even though the water is really not that super transparent like with some nice purigen filtered high tech tanks.

Anyway, I recently dumped some peat in the filter and I really like the brownish water color it made .


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## mysiak (Jan 17, 2018)

I am not aware of any other change than the removal of Purigen from the filter. I am still using the same ferts regime, the same filter cleaning schedule, the same type/amount of food etc. I noticed damaged leaves maybe after about a month after I added Purigen. After the removal, it took about 2-3 weeks for plants to "recover" (damage stopped spreading to new leaves). Changes were probably faster, but by this time they were clearly visible and wide-spread. 

My nano tank has standard soil, the bigger one just combination of aquatic substrates which is not a soil in the traditional terms (though probably "close enough"). "P" deficiency is similar to the lack of "N", so I might have misinterpreted the malnutrition cause. The only thing for which I'm quite confident is that I was experiencing a lack of mobile nutrients. CO2 could be a factor in the nano tank as I have a minimal water movement in there, but big tank uses air diffuser and heavy surface agitation, so I guess that any excess CO2 just dissipates. I will probably repeat the experiment with Purigen after some time again just to verify that it really has this kind of impact.

In each case, I am learning to like my yellowish/brownish water again


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## mysiak (Jan 17, 2018)

Did the test again, with the same result. Just in 2 or 3 weeks after the addition of Purigen, most plants started to have holes in the oldest leaves and yellowing of younger leaves. Green spot algae is almost fully covering old leaves. Fresh growth isn't visually impacted. Floaters are showing deficiency in old leaves and new growth as well. NO3 is pretty constant between 20-40ppm (tap water has ~30ppm) with or without Purigen. I do not have tests for Phosphorus, but I suspect that it dropped to almost zero with Purigen in the tank. 

Am I really the only one having issues while using Purigen in a NPT? Internet search shows only praises for Purigen which is a bit strange.


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## zolteeC (Dec 26, 2017)

mysiak said:


> Did the test again, with the same result. Just in 2 or 3 weeks after the addition of Purigen, most plants started to have holes in the oldest leaves and yellowing of younger leaves. Green spot algae is almost fully covering old leaves. Fresh growth isn't visually impacted. Floaters are showing deficiency in old leaves and new growth as well. NO3 is pretty constant between 20-40ppm (tap water has ~30ppm) with or without Purigen. I do not have tests for Phosphorus, but I suspect that it dropped to almost zero with Purigen in the tank.
> 
> Am I really the only one having issues while using Purigen in a NPT? Internet search shows only praises for Purigen which is a bit strange.


Most of the P is in the soil in NPTs..
I would be interested to see what happens if add peat in the filter with Purigen. When plant growth stalled in one of my mature NPTs, I put some peat in the filter (in stockings) and plant growth resumed. I guess Purigen would need much more frequent cleaning with peat, but on the other hand there may be good amount of CO2 released as peat decomposes even though DOC is removed by purigen from the water column.

Did you try to dose K + micro ferts with Purigen in? (Holes in leaves is often K deficiency....)


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## mysiak (Jan 17, 2018)

If I remember correctly, soil initially contains a lot of N and P (+ other nutrients), but they are depleted over time (~6-12 months) and then plants rely on nutrients from fish food and fish waste. Depending on tank (plants, livestock, lights etc), micro nutrients might need to be dosed extra after this time (my case). With Purigen, we are removing (almost) all organic waste which would be otherwise converted to N and P available to plants. I don't know how and if potassium is bound to organic molecules and if it's being removed by Purigen as well. 

I am dosing micro ferts which contain potassium (Seachem Flourish and Easylife profito before) at about 200% of recommended dose. This is enough when I'm not using Purigen, but not when I have it in the filter. I'm afraid to up the ferts more as I don't want to overdose the tank with some nutrients. 

I clearly don't know for sure what exactly happens when I use Purigen. But so far all my attempts ended up with the same result - clean water and damaged plants. If I need to dose macro ferts as well, I honestly see absolutely no point in using Purigen. Maybe just for a few hours per week/month to clear the water, but that's not very convenient. 

Combination of peat (or any tannins releasing substance) results in clear water and heavily discolored Purigen. It is just too good in removal of organic molecules..  I'm sure it's great for bare tanks and for them I would highly recommend it. I'm just not sure about usage in NPTs.


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## zolteeC (Dec 26, 2017)

mysiak said:


> If I remember correctly, soil initially contains a lot of N and P (+ other nutrients), but they are depleted over time (~6-12 months) and then plants rely on nutrients from fish food and fish waste. Depending on tank (plants, livestock, lights etc), micro nutrients might need to be dosed extra after this time (my case). With Purigen, we are removing (almost) all organic waste which would be otherwise converted to N and P available to plants. I don't know how and if potassium is bound to organic molecules and if it's being removed by Purigen as well.
> 
> I am dosing micro ferts which contain potassium (Seachem Flourish and Easylife profito before) at about 200% of recommended dose. This is enough when I'm not using Purigen, but not when I have it in the filter. I'm afraid to up the ferts more as I don't want to overdose the tank with some nutrients.
> 
> ...


To me it really sounds that you are not seeing a nutrient deficiency issue. As you mentioned, you have reasonably high NO3 in the water column (in my NPTs I usually cannot measure any NO2, NO3 or NH4 in the water column, still plants are in good condition.) and as you say you also dosed K + micro ferts, so there should be enough of this. I have never ever dosed P(hosporus) in my NPTs, I guess its quite rare that P is missing for rooted plants (soil usually contains tons of those, and fishfood also.)

So my theory (which is not on solid ground  ) is that Purigen cleans DOC from water column very efficiently and as this potential carbon source is removed from the tank, plants suffer. If this is the case, then impact on mature NPTs may be more severe as fresh soil in newly established NPTs release much more CO2.

This is why I was thinking about the peat addition to the filter, where oxygen rich water flows through it. Idea is to somehow counter balance the effect of DOC removal. As peat contains lots of C, and microbes and who knows what decomposes it, it releases CO2. On the other hand, Purigen may keep the water column transparent and -hopefully- not impacting the peat decomposition (?).

This above is pure guessing, I really have no clue about Purigen and its impact on NPTs.


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## mysiak (Jan 17, 2018)

Let's imagine this hypothetical scenario. Purigen removes 100% of organic molecules containing N and P (fish waste, fish food). Isn't it essentially the same as if we would have a planted tank with no livestock and no external input of most of the nutrients? At some point, plants would consume everything available in the soil and would start showing one or several deficiencies. 

Lack of carbon might be a factor too and sounds plausible, but floating plants are impacted as well, so it can't be only it. I still believe that Purigen indirectly removes one or more key nutrients, just don't know which exactly  

My main suspect (except carbon) is P, because:
- I should have plenty of N as even my tap water contains it and I can measure it
- I dose Iron, Potassium and other micro elements regularly and as Purigen does not remove inorganic molecules, it should not touch them
- missing nutrient is most probably mobile, as it impacts mostly old leaves

To my best knowledge, it leaves only Phosphorus. Surely I could miss something in this thought experiment, but without proper water analysis it's all I have 

Regarding peat - Purigen removes tannins really well, I'm not sure if it would leave enough of DOC for sufficient CO2 production. Also it would exhaust extremely quickly (matter of days, max few weeks vs months in "normal" usage). Using source of carbon with no tannins (rice as mentioned in one topic on this forum) is probably better idea if one wants to keep clean water.


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## zolteeC (Dec 26, 2017)

mysiak said:


> Let's imagine this hypothetical scenario. Purigen removes 100% of organic molecules containing N and P (fish waste, fish food). Isn't it essentially the same as if we would have a planted tank with no livestock and no external input of most of the nutrients? At some point, plants would consume everything available in the soil and would start showing one or several deficiencies.
> 
> Lack of carbon might be a factor too and sounds plausible, but floating plants are impacted as well, so it can't be only it. I still believe that Purigen indirectly removes one or more key nutrients, just don't know which exactly
> 
> ...


Thank you for clarifying your line of thinking. Probably I was really underestimating the chance of not enough available P, - partly because I have never ever dosed P and still tons of plants grew in my NPTs in the long run.
As you mentioned, floating plants are also impacted in your case. This is really pointing in the direction that some nutrients are not available in the water column. Anyways, it may also still be possible that floating plants and rooted plants suffer for different reasons. (i.e available C for rooted plans, lack of nutrients for floating plants.)

Maybe you can give a try to dose P in the water column and see what happens? It's a bit risky with a display tank, you may get tons of algae or who knows what .
The rice thing is also interesting, maybe I will set up a test tank to experiment (without purigen).


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## mysiak (Jan 17, 2018)

Most of plants with deficiency symptoms are fast growers and they are not rooted (just floating above the substrate). Only crypts jungle is rooted and it takes more time for them to react to the change. Even if there was some P left in the substrate, I must have nutrients in the water column for majority of my plants..  

I could probably start monitoring P with and without Purigen, but the test is a bit expensive and I can't think of any other reason why to purchase it. Depending on results I might dose P (which I would have to buy as well).. Or, I'll just keep Purigen away from my tanks and continue using fish food as the source of macro nutrients  (at least until I find a cheap way for complete water analysis).

I do not really need Purigen, there is nothing to be "fixed". I just read at many places that DOC is bad for the tank/livestock/plants and should be removed. And as mentioned before, absolutely clear water is really nice to look at. But probably just not worth the troubles, at least in my case.


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## tiger15 (Apr 9, 2017)

DOC is a catch all term of many different types of dissolved organic compounds. Some complex organic compounds, such as phenols and tannic acid can make water yellowish, so removing DOC by Purigen can clarify water. High DOC, similar to high nitrate, is an indicator of general pollution, as some compounds are toxic to fish at high concentration. I also read that high DOC can trigger algae, so heavily stocked tanks can become an algae farm unless DOC are removed by Purigen as recommended. Barr has done an experiment to add more and more minors to a planted tank and eventually algae popped up. There is a theory that algae can feed directly onDOC, but I haven’t found it the case as I have a heavily stocked cichlid planted tank with no algae when the plants are healthy. I do not use Purigen, but do 75% water change weekly in my high tech tank, but the average DOC and nitrate stay high due to heavy stocking. In low tech tank, it may not work.


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## zolteeC (Dec 26, 2017)

tiger15 said:


> High DOC, similar to high nitrate, is an indicator of general pollution, as some compounds are toxic to fish at high concentration. I also read that high DOC can trigger algae, so heavily stocked tanks can become an algae farm unless DOC are removed by Purigen as recommended. Barr has done an experiment to add more and more minors to a planted tank and eventually algae popped up.


I've found an interesting reading that shows how essential DOC can be for fish survival under specific conditions.
For example, Amazonian Rio ***** is a very acidic environment, and blackwater DOC protects fish from going belly up in this harsh environment.
https://www.nature.com/articles/srep20377
This source also points out that DOCs are not created equal as you mentioned. There are also lots of papers that discuss how DOC reduces toxicity of Copper, Aluminum, Zinc etc for fish (and shrimps)...

I can also see that DOC can be toxic. Say if I dumped a bottle of vinegar into the tank, I am sure fish would not be that happy.


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## dwalstad (Apr 14, 2006)

zolteeC said:


> I've found an interesting reading that shows how essential DOC can be for fish survival under specific conditions.
> For example, Amazonian Rio ***** is a very acidic environment, and blackwater DOC protects fish from going belly up in this harsh environment.
> https://www.nature.com/articles/srep20377
> This source also points out that DOCs are not created equal as you mentioned. There are also lots of papers that discuss how DOC reduces toxicity of Copper, Aluminum, Zinc etc for fish (and shrimps)...


Wonderful paper! Thank you for bringing it to our attention. One more reason to love DOC. 

Natural DOC compounds are produced by the decomposition of plant matter. DOC is not an indicator of pollution. The only _somewhat_ harmful DOC would be organic acids (acetic acid) released via fermentation in severely anaerobic substrates. They will inhibit plant roots.

DOC is a vital source of CO2 for NPTs. When you remove DOC, you remove a natural source of CO2. What's nice is that unlike artificial CO2 injection, the decomposition of DOC occurs at a slow and gentle rate. Won't kill the fish.

Hobbyists with high tech tanks remove all the plant nutrients with water changes, Purigen, excessive filtration/aeration. Then, they put them all back--at great cost--with fertilizers and CO2 injection.


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## tiger15 (Apr 9, 2017)

DOC can mean different thing in different setting. DOC in natural tannin tainted water is not harmful but beneficial to local fauna as it is a product of decaying vegetative matter. Blackwater fish keepers often use peat filtration to simulate tannin water to promote healthy growth and breeding. Amazon blackwater is actually low in DOC except that it is dominated by tannin. In urban or agricultural lands, high DOC typically means human pollution from runoff that can lead to eutrophication or oxygen depletion threat in low flow conditions as high DOC equals high BOD. In a NPT, some DOC is good as a source of carbon and nutrients for plants, but too much DOC often means over feeding, over stocking or lack of WC that is bad for plants and fish. A balanced NPT has light stocking but many hobbyists, like me, overstock.


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