rhodophyta

That theory might get some support from the people who dose their unplanted fish tanks with hydrogen peroxide to "bleach" the algae. Once the algae turns white, it rarely returns. A higher oxygen level in a planted tank might just work the same way bleaching the chloroplasts out of the algae cells.

 

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standoyo

I think this article about BGA is the best one yet and provides insight from a time before Oxygen was abundant on earth. http://www.skepticalaquarist.com/docs/algae/cyano.shtml

apistaeasy

I think this discussion has stepped away from the original question a little too far.

Recently most posts have been discussing cyanobacteria, which is not algae, but instead a photosynthetic bacteria. Applications that relate to plant and algae competition do not necessarily apply to bacteria. I believe that a discussion about cyanobacteria and plant competition belongs in another thread.

In regards to allelopathy. It is my understanding that allelochemicals actually work through bacteria. In this way, if allelopathy were occuring in our tanks, we should actually be looking at the way bacteria and algae compete for the same nutrients.

Also, in response to a comment on hydrogen peroxide. H2O2 kills algae not by raising O2 levels, but by oxidation in the same manner hydrogen peroxide kills bacteria in a wound. Algae is more susceptible to H2O2 treatment because of thinner cell walls than plants. Plants can be killed in the same way if their cell walls are thinner, like mosses or damaged parts of a leaf.

Interestingly on my local forum we have recently been having a discussion on the same topic. Here are my thoughts:

I believe that there is a critical balance between light, CO2, nitrate, phosphate, and traces (I'm including potassium in traces here). When something happens to change the balance algae sense the balance. This tip on the balance tells, or signals to, the algae that this is their time to have the outbreak we all hate.
I don't really believe there is such thing as an algae free tank. All the algae are there, they are just in a dormant phase. When a specific type of algae finds the conditions it likes it goes nuts. Some algae like low phosphate - GSA (green spot algae), some algae like low nutrients - staghorn, and some algae like almost every kind of imbalance we can create.
For each person their is some sort of unique imbalance that they create with their dosing schedule. For me it's GSA. My home tank has plenty of light (4.5 wpg), plenty of ferts, very healthy plants, is mature, hasn't had a water change in almost two months and is doing great with the only exception that every couple of weeks I start seeing typical GSA spots on the glass. My dosing schedule in the show tank at work is conducive to hair algae (I believe this is due to a low N:P ratio, and in my case it's 'cause the P is too high).
Take an example from nature - algae blooms often happen in streams and lakes where runoff from fertilized farms contaminates the perfect balance. The imbalance usually comes from phosphates. An algae bloom results.

So, to sum things up a bit...I believe the best way to keep algae at bay is to simply keep a proper ratio of light, CO2, macros and traces.

fastang80

Nice thread. Very informative.

 

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