I don't think the existence of allelopathy in aquatic plants is a hypothesis. I believe adequate research has been done to prove it's existence. The question is, does it play a role in the plant/algae competition in a planted tank. My hypothesis is yes, but to such a small degree to be insignificant for our purposes. This debate seems to be of little value as far as the goal of keeping healthy algae free plants in an aquarium. The fact of the matter is that it's done everyday. If allelopathy was the primary reason for algae free tanks we would have problems after changing water, using activated carbon, keeping multiple varieties of plants together and even keeping certain invertebrates as allelopathy can effect lower life forms as well. Algae scrubbers would fail as a result of algacidic compounds released by plants. This is not the case.
The debate always seems to start over the hypothesis of competition of plants versus algae for nutrients and light. Since nutrients and light are abundant in a healthy planted tank it cannot be a competition. Both algae and plants are provided with excess of each. So this simplistic view doesn't hold water either. That's the primary reason I began searching for other causes.
I prefer to follow Occum's razor when dealing with problems. It states that among competing hypotheses, the one that makes the fewest assumptions should be selected. In 20th century language “KISS”, keep it simple stupid.
Using that logic let's visit the competition hypothesis. As I said nutrients and lighting are in abundance so algae and plants cannot be in competition for those nutrients. The obvious answer must be the form of nutrients we use. It's a fact that those nutrients are primarily inorganic compounds otherwise activated carbon would strip most of them away. When do we see algae blooms in a healthy planted aquarium? Disturbing the substrate, failure to remove decaying organics, too much light in a sparsely planted tank and over feeding all seem to be a common theme.
So it's my hypothesis that competition does exist but rather a competition for organic nutrients The problem arises when the competition hypothesis is explained. When we increase the organics we see algae blooms. The inorganics we use as nutrients must not be readily utilized by algaes we see. So the confusion comes when we don't preface the competition hypothesis by saying the nutrients we add are inorganic and are not involved it that competition. At least that's my hypothesis today.
PS Hoppy did you like the use of hypothesis rather than theory? lol
Last edited by Zorfox; 04-03-2013 at 05:08 PM..
Reason: spelling errors