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Old 09-12-2013, 12:26 PM   #1
Qwe
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Allelopathy and BGA


So I've been rereading my copy of Diana Walstad's Ecology of the Planted Aquarium, and in her chapter on allelopathy, she points out several allelochemicals that inhibit cyanobacteria. So I'm curious if anyone has tried introducing plants with certain allelochemicals to combat BGA? If so, what plants and did it work?
It would certainly be an interesting experiment if nothing else...
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Old 09-12-2013, 02:04 PM   #2
micheljq
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Hello, I did read Diana's book, great read.

I did fight cyanobacteria since I did began having planted aquariums 2 years ago. In fact, I had cyano in all my setups, having serious invasions at time.

I trust allelopathy works over time. I remember Diana mentionning "mild allelopathy" in his book.

I my case I do complete fertilisation through the water column and it's helps the plants a lot. At one point plants and cyano grow quite well together at the same time. I remove the cyano regularly, it's easy to remove by siphonning or with a fish net. Over time the cyano disappears by itself. In my last setup, low light, with ferts, it took 4 months to disappear. I had fast growing plants like limnophila sessiflora, ceratopteris thalictroides, & egeria densa.

I have moved my tank recently, it's in water since august 18th. I have CaribSea Sunset gold sand mixed with seachem flourite. This time I did add only 1,5L of Miracle Gro potting mix below the substrate. It did give a serious boost to the plants (limnophila sessiflora grows agressively, i did already begin to trim it regularly a week ago, if I do not it will cut the light of my bacopas monnieri, which grows slower).

I have some cyano too, but scarse. Probably that cyano will expand since the tank is young, but for me it is the way of things, it's normal in the beginning.

I did never use blackouts, or anti-algae chemicals. I believe well maintained plants will keep algae in check but you need patience, it normally takes many months.

Michel, hope it helps.
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Last edited by micheljq; 09-12-2013 at 02:13 PM.. Reason: typos
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Old 09-12-2013, 05:03 PM   #3
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http://www.bio-web.dk/ole_pedersen/p..._2002_15_7.pdf

I made the case maybe 15 years ago now that higher density of well growing submersed plants will deter algae regardless of the plant species (we keep nearly 400+ species and varieties).

Now given this observational fact(seen in nature as well as aquariums), the likelihood that that ALL 400 species ALL possess the same chemical and impact on algae seems statistically improbable. As in Billions to one chance and I am being generous with the error that it might be possible
That alone is strong reason to doubt all on it's own.

In vitro test wells, ground up mashed extract are VERY different than real living intact plants. You cannot say it'll be the same in situ. the next stage would be trying to detect those chemicals and their impacts on live plants, algae in the natural conditions of interest.
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Old 09-12-2013, 06:00 PM   #4
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Yes, high plant density deters algae, especially because the plants use the nutrients that algae would need to grow, chemicals aside. I don't see how that provides any evidence for or against allelopathy...
Anyway, BGA is not algae... and I'm not looking for methods to rid my tanks of it, but actual experiences people have had with certain plants and BGA.
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Old 09-12-2013, 06:11 PM   #5
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Quote:
Originally Posted by Qwe View Post
Yes, high plant density deters algae, especially because the plants use the nutrients that algae would need to grow, chemicals aside. I don't see how that provides any evidence for or against allelopathy...
Anyway, BGA is not algae... and I'm not looking for methods to rid my tanks of it, but actual experiences people have had with certain plants and BGA.
No, plants do not use up all the nutrients. We can easily add plenty of ferts for both the plants and the algae, algae are never limited in any planted tank.
Clear examples are found going back decades, simply google my tanks here or elsewhere on line. Videos etc.

If you cannot see why allelopathy is NOT present in aquariums, then you need to sit down and read more and think about the logic behind it. Then after that, what type of "control" might you use to test whether or not allelopathy exist in a planted tank in situ?

If you add activated carbon to a planted tank, then this will remove the allelopathic chemicals. The hypothesis is that these chemicals retard/inhibit/ stop/prevent algae. So removing them should lead to algae.

However, activated carbon has been used for many decades in the hobby and has never found to induce any algae in planted tanks. the opposite in most case, cleans the tank up more and less algae.

So there's not 1, but 3 points against allelopathy.
1. Research does not support it.
2. Statistically improbable based on observations.
3. Experiments can be done and have been done that demonstrate it does not occur using real intact planted tanks.


Other than wishful thinking, what support can be offered for allelopathy?

If you wish to be specific, Oscillitoria is the genus that infest our aquariums. I identified this genus as the genus of interest for aquarist back in 1999.
It's not hard to get rid of frankly.

As far as plant species with and without it, that would be pretty much all plants, all 400+.
Like I said, the statistical evidence/hobbyists observations over many decades cannot support allelopathy.
Do not say someone did not tell you.
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Old 09-12-2013, 07:58 PM   #6
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Have you also thought that maybe a well mature bacterial population can also deter BGA? BGA almost always occur in new tanks.

Add water movement and lower the light intensity also helps regardless of plant population.
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Old 09-13-2013, 10:26 PM   #7
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Well thank you, the article you linked provides exact plant species (Myriophyllum spicatum) that produced allelochemicals which inhibit BGA as per Gross's experiment.
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Old 09-13-2013, 11:44 PM   #8
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Unfortunately it's also highly invasive and on several states' lists.
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