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In the last 3 years I've had 4 tanks that were either free of algae or the algae was a direct result of something I did and the problem easily corrected. My opinion is not directly related to EI or PPS but I hope it has some merit. I'd say that in all 4 cases the plants had an "advantage" at some point and they "took over". How did the plants get ahead and how they maintained their dominance I can't say. Here are my assumptions;

Tank 1
Densely planted 55 gal. with extremely vigourous plants from the very beginning. The plants were grown for about 3 weeks in an unsual environment were they reproduced at almost insane rates. After transferring them to a tank containing 100% new Fluorite they continued the fast growth, but not at the same rate. About 2 sq. inches of hair algae appeared about day 5 and a blackout took care of them. The tank ran for about 6 months with no algae whatsoever, no fertilizing of any kind the first 3 months, and very lean additions of N and P later (NO3=2-3, PO4=0.25, 1 ml. of Fluiorish every 4-5 days). Water changes - 5 gals every week.
Assumption, advantages for the plants
The plants had the advantage of being very strong, not transported for days, and functioned 100% from the very beginning.

Tank 2
100% RO and 100% garnet (inert gravel, very much like glass). The algae appeared only if I overdosed a little or if I neglected to dose. Very lean dosing of N, P, Fe, Mg, and Ca.
Assumption, advantages for the plants
The fast growing wisteria in that tank used up all the available nutrients (not that much to start with)
The light was rather low - glosso would always try to grow vertically.

Tank 3
110 watts over a 25 gal., EcoComplete, Peat, Dupla Baccies. Narrow Leaf Java Fern, Anubias, Glosso. GH of 13 due to the EcoComplete. Very little fertilizing amounted to pale plants but no algae at all. Adding small amounts (N=3, P=0.25, Mg to bring the GH to 16, 10 drops Fe/TE daily) of PPS fertilizers and reducing the light period from 10 to 7 hours resulted in explosive growth. Only adding PPS fertilizers did not improve the situation. Algae (BBA, Staghorn) took over when I let the tank evaporate 50% but never appeared again when resuming good care.
Assumption, advantages for the plants
Luis magic hand.
Strong light limits algae, almost sterilizes the entire tank, but plants survive.

Tank 4
5.7 wpg, 100%RO, 100% garnet. Very little fertilizing in the beginning. Severe pale growth. No algae at all. Adding PPS fertilizers up to NO3=10 and PO4=0.5 + Fe/TE and Ca/Mg did not improve the plants. Reducing the light period did not change anything either.
Reducing the light to 3 wpg resulted in explosive plant growth even with no fertilization at all. No algae at all.
Assumption, advantages for the plants
Lack of nutrients limited the algae but the plants grew (pale).
Strong light limits algae, almost sterilizes the tank.

That's all folks!
--Nikolay
 

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plantbrain said:
Folks considering algae not growing at higher nutrients may want to look into what a niche is and compare enzyme kintetics=> this is directly influences uptake rates and competition with plants.
But why would nice and high nutrient levels (especially N), that drives the plants Vmax higher in plants than in algae through efficient Enzymes, inhibit algae?

I understand that plants can't survive the low nutrient levels that algae can (niche concept), but I can't see why healty plant leaves with good light and good nutrient levels doesn't act as an algae-collector? Everything exists on a healthy plant leaf: Very good light and very good nutrient levels?

Or does high and efficient plant uptake rates means the water above the leaves are totally nutrient deficient?
 

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"allelochemical" in some circles seems to be about as controversial as Plocher's ideas. I've never seen any report on observed allelochemical activity in aquarium plants. I've noticed that when certain plants get to a critical biomass in an aquarium, they tend to take over and other plants tend to take on a recessive mode, until they in their turn enjoy a dominant period. But would that be what we might call allelochemical activity?

The idea of allelochemical implies that a plant has a defense mechanism, a sort of immune system analgous to the one we know and love in our own bodies, and that if the plant is not properly fed its immune system declines rapidly allowing algae to take over.

Andrew Cribb
 

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Andrew,

There is a growing body of scientific work on allelopathy in aquatic plants. Allelopathy has been known for many, many years. I think the term was coined in 1937. Allelopathy in terrestrial plants has been well documented and is scientific fact. There have been studies on Myriophyllum spicatum, Cattail, Lemna minor, nuphar lillies, hornwort to name a few.

Diana Walstead has a whole chapter devoted to it if I remember correctly and Ole Pedersen refuted many of her claims in an TAG article that you can now read on Tropica's website.

There are also studies on the impact of stressors on allelochemical production. So you immune system analogy is not too far off.
 

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pineapple said:
The idea of allelochemical implies that a plant has a defense mechanism, a sort of immune system analgous to the one we know and love in our own bodies, and that if the plant is not properly fed its immune system declines rapidly allowing algae to take over.

Andrew Cribb
I think it is the allelochemicals and the plant immune system that keeps algae away. Only healthy plant can produce enough toxins to kill the algae around it.

Edward
 

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Art said:

Good plant growth = algae limitation BECAUSE:

1) Good plant growth results in limiting a key nutrient for algae; or
2) Good plant growth produces some sort of allelochemical that limits algae?
There is a third possibility---Good nutrient levels make nutritious algae, and the animals that eat the algae thrive and multiply and eat it all up. Poor nutrient levels result in algae so low in nitrogen that herbovires get no food value by eating it. Also, when nutrient levels are low, the algae may be able to put more of its photosynthetic effort into producing toxins that protect it.

It is important to distinguish what kind of algae we are talking about. Green water, Cyanobacteria, Red algae, Oedogonium, Cladophora, Rhizoclonium, green spot algae, etc.
 

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HeyPK said:
There is a third possibility---Good nutrient levels make nutritious algae, and the animals that eat the algae thrive and multiply and eat it all up.
Paul,

Can you take this idea a bit further?

I have noticed that when my tank slips into its tip-top sweet spot my ottos have to really work hard to fill their bellies. When I'm off target they have nice round tums and lounge around or play.
 

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I have seen that various forms of bluegreens (Cyanobacteria) get started when nitrogen is low. They are not very green and are not so noticable. Snails are on the decline while this is happening. If I give a good shot of nitrients, the bga suddenly becomes very visible as it greens up, but then the snails start perking up, growing and eating it. Somewhere, a long time ago, I remember seeing a paper that claimed that many types of algae have a very wide range of nitrogen content, depending on nitrogen availability, ranging from too low to be of food value to quite high in protein.
 

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Personal Epiphany?

After reading and re-reading numerous threads here, I have come to a few conclusions..............

Algae all need the same elements to thrive, though some do it better than others. I ASSuming this is why you can't differentiate why each one shows up in your tank. (IE........bba is caused by excessive... and green fuzz algae is caused by...) I do understand that it has to be introduced into your tank to begin with (ie new plants or fish).

CO2 increases plant growth which in turn allows plants to outcompete algae (Still don't know why increased plant growth means little algae if algae needs very little nutrients to the point where they are immeasureable on our test kits).

With this in mind, why doesn't algae always show up in tanks (or at least more than we see in healthy aquariums?)

IF one takes into account the theory of survival of the fittest (Usually the simplest creatures survive) Then why do blackouts work?

I'm really interested in everyone's opinions and theories.
 

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Simpte 27 said:
IF one takes into account the theory of survival of the fittest (Usually the simplest creatures survive) Then why do blackouts work?

I'm really interested in everyone's opinions and theories.
Well, here is an opinion from me on blackouts...Maybe the blackout doesn't kill the algae at all! Maybe it only causes it to go dormant. Kind of like trees loosing their leaves in the fall when the days get shorter. Maybe the lack of light is a signal for the algae to go into a resting period. Then add in the fact that after most blackouts a water change is done along with some pruning. Maybe the 'dormant' algae settles on the substrate and plant leaves and is siphoned off during the water change...

Just a thought...
 

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Simpte 27 said:
CO2 increases plant growth which in turn allows plants to outcompete algae (Still don't know why increased plant growth means little algae if algae needs very little nutrients to the point where they are immeasureable on our test kits).

With this in mind, why doesn't algae always show up in tanks (or at least more than we see in healthy aquariums?)
I believe this goes with opportunistic organisms versus equilibrial organisms. Opportunistic organisms are found in variable environments where their population densities fluctuate. Algaes tend to be more opportunistic in nature. They are capable of reproducing quickly when the given opportunity arises and overtake an area quickly. However, when resources run low and population sizes reach an environment's carrying capacity, then equilibrial organisms tend to dominate. Equilibrial populations can better utilize resources and have slower reproduction rates that can be maintained at a more constant population size specifically at the carrying capacity of an environment.

In a sense, algae will only dominate (ie. algae blooms which can last forever) when nutrients are not in balance. The issue of nutrients, I believe, varies from tank to tank though. Higher-order plants help to compete against algae since they can better utilize the resources at lower levels and prevent algal blooms by keeping the water nutrients trim. In biological terms the plants' population density is maintained at the carrying capacity which you set for the tank depending on the amount of nutrients, space, etc. available. Algae density populations have difficulty being maintained at the carrying capacity of an environment because of their opportunistic tendicies to reproduce quickly.

Simpte 27 said:
IF one takes into account the theory of survival of the fittest (Usually the simplest creatures survive) Then why do blackouts work?

I'm really interested in everyone's opinions and theories.
Survival of the fittest works for all aspects of nature and is not limited to the simplest creatures surviving. I don't believe that survival of the fittest pertains to artifical conditions since it is a theory that discusses the maintenance of a specie's genes through natural adversities as opposed to the specific eradication of a type of organism by artificial means.

As matpat discussed, different algaes have varying life cycles. Although the only algae (which it isn't) I know of to undergo a dormant period is BGA. Other algaes I don't know about but would gander to say that they don't have dormant periods. BGA is a bacteria which is capable of entering a phase in its lifecycle as is most bacteria in a state of dormancy during times of extreme conditions including dehydration and extreme heat. I don't believe a blackout will conduce it to undergo a dormant period though.

Too many factors exist for us to say why some algaes can and others can't survive a blackout. Some algaes might store more energy than others. Some algaes might utilize the littlest amount of light entering the tank during a blackout better than others. I don't believe most lower-order plants can enter a dormant period, though, but I might be wrong. The possibilities of "maybe" and "what if"'s are endless and sadly I believe this is true for much of the hobby.
 

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This makes a lot of sense... then this means that when the equilibrial organisms (the higher order plants) dominate, the opportunistic organisms (the algae) diminish in population to the point where they are not very visible?

I like this explanation. It re-enforces what I've always believed: take care of the plants and the algae will loose the battle.
 

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I do believe there is more to it then just the proper inorganic fertilizer presence. The post number 27 in this thread by HeyPK may point us to the right direction. Most likely there are some microorganisms helping in algae elimination. I have tried to break in new sterilized aquarium setups without root transplanting and with sterilized substrate to find never-ending disappointment. Once, roots or old substrate was added, aquarium turned crystal clean.

Edward
 
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