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Discussion Starter #1
I believe most of us have noticed that in some planted tanks there is a time when the algae completely disappears. That disappearance is not a result of any nutrient, filtration, light, or other manipulations. It feels like the the algae simply "gives up fighting" at that point. There is enough of everything we are aware of for the algae to continue fighting.

One can achieve that by just letting the algae grow if they are not too bad and not cleaning them at all. I've had about 3 cases of sudden algae disappearance like that and it happens very quickly - in 1 to 2 days only. These have been tanks with a variety of plants which thrived and grew explosively with a lot of light and nutrients in the water column.

In one tank I stopped dosing and the light was reduced to about 40% of what it originally was because the stem plants took over the surface. Water changes were done only when the evaporation reached about 10% of the tank volume. The water was slightly yellowish at all times (organics?). This slow but drastic change of conditions did not change anything - algae never appeared again. Shutting down the CO2 slowly brought BBA, BGA and even some hairalgae.

One final observation note - such tanks are quite hard to knock off balance. Overfertilizing is not an issue. High Phosphate and low Nitrate are not an issue. Running the tank very lean doesn't lead to any problems either. Perling continues for about 7-10 days without adding any fertilizers.

What would be your explanations/speculations on those observations?
What is the difference between and established and a new tank?
Why would algae quickly leave a tank full of nutrients in the water, never vacuumed substrate, tons of light and CO2?

--Nikolay
 

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Why would algae quickly leave a tank full of nutrients in the water, never vacuumed substrate, tons of light and CO2?

We'll you mentioned earlier that the plants covered the surface. I think this makes a big difference, a lot less light gets through. The plants take C02 from the atmosphere, giving them the advantage to take up nutrients quickly.

What is the difference between and established and a new tank?

Same as before, ammonia is sucked up so fast that algae can't grow. There was a really good article I read that described how much a difference in plant density makes. If you think about it, every leaf on your stem plants is a spot that bacteria can use to grow on and absorb ammonia. The amount of surface area from an established tank compared to a new tank is completely different. Your established tank becomes one big filter that starves out the algae.
 

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I can't explain it, but have thought of it as a process of innoculation. The system is infected then developes an immunity. Some things are hard to explain, for example in that post in which you (Niko) noted that the glass exposed to air during a water change does not develop algae again, or that Anubias exposed to air in the same process do not get algae.

The mysteries of life remain hidden in our crystal boxes..

Andrew Cribb
 

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In Diana Wasfield's book there is a chapter on alochemicals, it says that all aquatic plants leach out a chemical (or many chemicals) that inhibit algae, and some plant types. That could help explain it, and why a plant will grow fast in one tank, and grow very slow or not at all in another.

Whiskey
 

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Discussion Starter #5
My response to the bacteria, immunity, and allelochemicals would be:
Why don't they develop/are released say 3-4 weeks from setting up the tank?

If conditions are good after 3-4 weeks the plants certainly look established, should have strong immune system, and shoot alellochemicals all over the place. Immunity - at least one of the ADA products deals with immunity, correct? Allelochemicals - I personally believe they exist but some people surely don't.

The bacteria - they multiply horribly fast and eat NH4 horribly fast... but not in the first few weeks? I am inclined to believe that bacteria has a great role because 2 of my tanks that were setup with a lot of commercial bacteria had and have no algae problems whatsoever.

Only one of my 3 tanks ended up having plants blocking the surface. The algae disappeared before the plants reached the surface and blocked the light. The other 2 were always exposed surface and the algae still disappeared.

--Nikolay
 

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Maybe there is another kind of bacteria. Fogure the leaf surface is a great place to grow bacteria. Why wouldn't there be some kind of bacteria that sets up shop on the leaf once it's settled in the aquaria, that benefits from keeping algae away?

-MT
 

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I think its the amount of root mass. An established tank can have a significant amount of root biomass to hold/absorb nutrients. With that one can trim the stems all day long and still have a significant amount of plant matter to soak up nutrients.
 
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