# A secret to preventing algae



## Unlimited16 (Feb 21, 2016)

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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## azazan (Aug 17, 2014)

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


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## Aqua Hero (May 8, 2015)

Youve only had co2 for a week? I would wait a bit longer to see whether it's true or not

Sent from my D2303 using Tapatalk


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## Unlimited16 (Feb 21, 2016)

apparently it only removes waste, and does not have an effect on anything else.


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## Straight shooter (Nov 26, 2015)

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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## s_s (Feb 15, 2012)

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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## Hoppy (Dec 24, 2005)

s_s said:


> 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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## Nordic (Nov 11, 2003)

Tetra's algumin product uses the humic acid method.... so that one seems legit.


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## Hoppy (Dec 24, 2005)

Nordic said:


> Tetra's algumin product uses the humic acid method.... so that one seems legit.


For some reason Tetra Algumin is not available in the USA, as far as I can tell. It would be interesting to find out why.


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## burr740 (Feb 19, 2014)

If Purigen cured the algae problem it is most likely because there was too much organic waste to begin with, and the Purigen reduced it.


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## alcimedes (Dec 7, 2014)

Hoppy said:


> 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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## TLE041 (Jan 16, 2010)

A tank that's been set up for less than 2 months is still too new. The algae still hasn't had a chance to get a foothold yet. I strongly doubt it'll be the same case in 6 months.


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## Straight shooter (Nov 26, 2015)

Allelopathy is real in aquatic plants but only has a very minor impact in our aquariums. Walstad confirmed this is true but did state that it only a small factor that isn't much cause for concern.


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## Zhylis (Nov 25, 2015)

Hoppy said:


> For some reason Tetra Algumin is not available in the USA, as far as I can tell. It would be interesting to find out why.


As far as I can tell, Tetra Algumin contains the herbicide/algicide monolinuron, which is a chemical that hasn't been registered for use in the USA.


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## Hoppy (Dec 24, 2005)

Zhylis said:


> As far as I can tell, Tetra Algumin contains the herbicide/algicide monolinuron, which is a chemical that hasn't been registered for use in the USA.


From http://datasheets.scbt.com/sds/WPNA/EN/sc-228613.pdf










This may be why it isn't sold here.


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## Zhylis (Nov 25, 2015)

Hoppy said:


> From http://datasheets.scbt.com/sds/WPNA/EN/sc-228613.pdf
> 
> 
> 
> ...


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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## Nordic (Nov 11, 2003)

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
> ...


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## s_s (Feb 15, 2012)

alcimedes said:


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


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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## mistergreen (Dec 9, 2006)

Seachem's excel does a good job as an algaecide.

There's no secret to algae prevention.


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## Hoppy (Dec 24, 2005)

s_s said:


> 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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## AWolf (Jun 13, 2014)

s_s said:


> 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.



Sometimes I feel the same. Thankfully there are enough of us out here willing to be open and explore possibility, and want to learn. Some responses to posters' on this forum are 'off putting', to say the least. It makes you want to go 'nevermind, sorry I ever said anything.' Cynical is the best word to describe them. I'm learning to ignore them, and engage with those who are open. If I don't believe something is possible, I prefer to say 'Interesting, I'll have to look into that.' I think it is good forum etiquette.


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## ichy (Apr 6, 2015)

burr740 said:


> If Purigen cured the algae problem it is most likely because there was too much organic waste to begin with, and the Purigen reduced it.


I run Purigen and still get hair algae.
What really helps keep my algae in check is to STOP dosing EI.


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