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So this just occurred to me when I had a friend ask me how my aquarium is so clear and free of algae, and I thought I'd share it. I've been using high lighting in my planted tank for almost two months now, and just recently started using CO2 a little over a week ago, and have never had an issue other than when I first set the tank up. I think the secret might just be the purigen I am using in my HOB filters? The tank has been setup for about two years now, and during the first 6 months I did have issues with nitrate and algae, and ever since I started using the Purigen, I've never had an issue with excessive nitrates and/or algae. Anyone else have any similar experiences with this product?
 

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I use this in my reef tank and it does the job pretty well.. in a planted tank it'd remove a lot of goodies for the plants, no?

In my experience algae can easily be prevented with correct dosing and CO2 if you have a high light planted tank, then again, I am happy it works out for you this way :p
 

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Pics or it didn't happen.

Purigen will remove organic compounds before they are able to degrade into ammonia, nitrite, and nitrate etc but will not directly remove them. It is very safe to use in planted tanks.

I've run Purigen for YEARS and still seen algae. It's job is to polish water nicely, particularly useful with tannin staining (leaching driftwood), not prevent algae so much. Just so happens it does have a potential role to play in reducing algae levels in terms of 'capping' nutrient levels so they don't build due to nitrification etc in combination with your dosing schedule.

I wouldn't bet on Purigen being the one factor that prevented algae in your case though.. Many other variables at play also.
 

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For the most part, algae comes and goes at random. The type of algae bloom you get is mostly random.

That said, we know of at least four factors that control algae:

1. Healthy plants produce allelopathic chemicals that are harmful to algae (and sometimes other plants).

2. Water high in humic acid (tannins) content creates conditions inhospitable to most algae (and most bacteria and many plants).

3. We also know that periods of low CO2 availability and high light are more beneficial to algae than plants.

4. We know that we can limit the position of some essential nutrients to the soil where plants (being complex organisms) have the ability to extract them and algae does not. Ferrous iron (Fe2+) is commonly cited as an example.

All common "systems" of keeping planted tanks use one or more of these methods directly or indirectly.
 

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For the most part, algae comes and goes at random. The type of algae bloom you get is mostly random.

That said, we know of at least four factors that control algae:

1. Healthy plants produce allelopathic chemicals that are harmful to algae (and sometimes other plants).
It has never been demonstrated that aquatic plants produce allelopathic chemicals, nor has it been demonstrated that if they do, the chemicals are effective against any form of algae, let alone all of the species that annoy us.
2. Water high in humic acid (tannins) content creates conditions inhospitable to most algae (and most bacteria and many plants).
I have never heard of this before. What is the source of this information?
3. We also know that periods of low CO2 availability and high light are more beneficial to algae than plants.
I think it is more accurate to say that fluctuations in the CO2 concentration in the water from day to day can lead to BBA, one form of algae. High light encourages growth of both plants and algae.
4. We know that we can limit the position of some essential nutrients to the soil where plants (being complex organisms) have the ability to extract them and algae does not. Ferrous iron (Fe2+) is commonly cited as an example.
Nutrients in the substrate can leach out into the water. Diana Walstad has said, as I recall, that nutrients are prevented from crossing the substrate/water boundary, but I have read that other experts disagree with this.
All common "systems" of keeping planted tanks use one or more of these methods directly or indirectly.
Algae is rarely a serious problem with low light tanks. When you have medium and higher light, algae become a potential serious problem. Using adequate fertilizing and consistent CO2 concentration from day to day, along with very good regular maintenance will go a long way towards avoiding those problems.
 

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It has never been demonstrated that aquatic plants produce allelopathic chemicals, nor has it been demonstrated that if they do, the chemicals are effective against any form of algae, let alone all of the species that annoy us.I have never heard of this before. What is the source of this information?
So I decided to do some digging, and it appears there is a variety of research on exactly this topic.

Allelopathy in aquatic environments may provide a competitive advantage to angiosperms, algae, or cyanobacteria in their interaction with other primary producers. Allelopathy can influence the competition between different photoautotrophs for resources and change the succession of species, for example, in phytoplankton communities. Field evidence and laboratory studies indicate that allelopathy occurs in all aquatic habitats (marine and freshwater), and that all primary producing organisms (cyanobacteria, micro- and macroalgae as well as angiosperms) are capable of producing and releasing allelopathically active compounds. Although allelopathy also includes positive (stimulating) interactions, the majority of studies describe the inhibitory activity of allelopathically active compounds. Different mechanisms operate depending on whether allelopathy takes place in the open water (pelagic zone) or is substrate associated (benthic habitats).
Study from above quote

Many of the papers I can't actually read though, since they're behind a paywall, but the abstracts seem to say that it's very real, and has been studied in aquatic environments.

Some of the research is 20+ years old it looks like.

http://rcin.org.pl/Content/47414/WA488_34078_P509_T18-1-PAH.pdf#page=19

Possible allelopathic effects of cyanotoxins, with reference to microcystin-LR, in aquatic ecosystems - Pflugmacher - 2002 - Environmental Toxicology - Wiley Online Library

Allelopathic Effects of Several Higher Aquatic Plants in Taihu Lake on Scenedesmus arcuatus Lemm.--?Rural Eco-environment?2001?03?

Some specifically look at algae inhibition.

ALLELOPATHIC EFFECTS OF SEVERAL AQUATIC PLANTS ON ALGAE--?Acta Hydrobiologica Sinica?1992?01?
 

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Actually the majority of herbicides have a similar Sec.12, which is why I cringe every time someone posts about using a commercial algicide in their aquarium. Sure, it'll kill the algae. And potentially everything else in the tank. But Tetra/Jungle/API sells it; it MUST be safe! >.<
 

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Tetra Algumin Algae Combat: Amazon.co.uk: Pet Supplies

When used correctly it is supposed to cause no harm...

Mild biological treatment for combating algae.

•For use at the onset of algae problems
•Broad-spectrum action to combat all frequently occurring types of algae
•Contains humic substances as a natural anti-algae agent
•When used correctly, it is harmless to fish, plants and micro-organisms
 

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So I decided to do some digging, and it appears there is a variety of research on exactly this topic.



Study from above quote

Many of the papers I can't actually read though, since they're behind a paywall, but the abstracts seem to say that it's very real, and has been studied in aquatic environments.

Some of the research is 20+ years old it looks like.

http://rcin.org.pl/Content/47414/WA488_34078_P509_T18-1-PAH.pdf#page=19

Possible allelopathic effects of cyanotoxins, with reference to microcystin-LR, in aquatic ecosystems - Pflugmacher - 2002 - Environmental Toxicology - Wiley Online Library

Allelopathic Effects of Several Higher Aquatic Plants in Taihu Lake on Scenedesmus arcuatus Lemm.--?Rural Eco-environment?2001?03?

Some specifically look at algae inhibition.

ALLELOPATHIC EFFECTS OF SEVERAL AQUATIC PLANTS ON ALGAE--?Acta Hydrobiologica Sinica?1992?01?
No surprise to me that your post has fallen on deaf ears. The primary trend in the discussion that happens on this forum is clearly to maintain the status quo and squelch out competing thoughts to the established systems. Probably to be expected since the research-minded tend to peruse research rather than post on ideological internet forums.

Engaging around here really seems to do no good.
 

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No surprise to me that your post has fallen on deaf ears. The primary trend in the discussion that happens on this forum is clearly to maintain the status quo and squelch out competing thoughts to the established systems. Probably to be expected since the research-minded tend to peruse research rather than post on ideological internet forums.

Engaging around here really seems to do no good.
Any allelopathic chemical would have to be an organic molecule, not inorganic, simply because organisms don't, as far as I know, manufacture inorganic compounds. Organic molecules are large molecules, easily removed from water with activated carbon. So, a good test for whether or not a planted tank is free of algae because of allelopathy by the plants would be to filter the tank water with activated carbon and watch the plants to see if an algae bloom results. The strong argument against allelopathy in planted tanks is that this has been tried by several people, with no algae blooms resulting.

A test of that type doesn't mean there are no species of plants that use allelopathy against algae, just that in a typical algae-free planted tank, no one has been able to show by this test that allelopathy is occurring.

Those papers about allelopathy do say the evidence of allelopathy was found, but for specific species only. We, who don't believe that allelopathy is a factor in our planted tanks, believe that it hasn't yet been shown that the species of algae and the species of plants we use are involved in such a relationship.

I don't believe there is the slightest chance that any of us wish to stifle anyone's ideas about how to avoid algae, given that algae is probably the single biggest problem we all encounter.
 
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