[MiamiAG]

The discussion on the PPS thread got me thinking again. I know it's been discussed before. I don't think we have a definitive answer so lets give it another whack, college try, that sort of thing...

New school fertilization methods (EI and PPS) have certainly deepened our understanding of planted aquarium nutritional dynamics. They have allowed MANY more people to enjoy algae-minimized tanks.

The question is: why do EI and PPS minimize algae?

 

[MiamiAG]

Thanks Alex!

I agree with you that using the new methods results in algae limitation. The question I have is WHY do they work? If plant's growing well = algae limitation AND if algae and plants need the same nutrients (careful, I didn't say in the same ratio, levels, etc.), then can I conclude the following?

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?

 

[MiamiAG]

I believe, correct me if I'm wrong, that the whole purpose of this thread is the question why this is true: Why does unlimited nutrients and happy plants keep algae at bay?

Correct!

There's a lot of very experienced and knowledgeable folks here. Let's hear your hypothesis, theory, conjecture, what not! You don't have to be right, just throw up your gut feeling.

 

[MiamiAG]

Why ask why?

Because it is key to deepening our understanding of planted aquarium dynamics.

 

[MiamiAG]

Hey TW, do you know Hanns-Jürgen Kraus? He's a person who suggested something similar to what you just did. Very controversial back in 1995-6. I have a few of his books and articles. We tried to get them translated and published here but it was a no go.

We discussed it on the APD back in 1997 if I recall. I remember Kaspar Horst of Dupla thought that Kraus' oxygen theory had been disproved. It appeared in Das Aquarium I think.

 

[MiamiAG]

Tom, does it then boil down to a competition between plants and algae? The reason people say you have more wiggle room with less light is that deficiencies can occur quickly when creating a high metabolic rate as is the case with higher light levels. This would imply that it's a nutrient competition thing again.

 

[MiamiAG]

Let me try to focus the conversation. Is it competition or is it allelochemical suppression that keeps algae at bay?

 

[MiamiAG]

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.

 

[MiamiAG]

Good point Paul.

 

[MiamiAG]

Unfortunately, Tom has decided to remove all his posts from this thread so we can't consider his opinions on this topic.

I, for one, find this topic interesting and feel that there isn't a true answer yet. I do hope that someone takes the time to study this topic in detail and post their experiment/findings so that we can get to a true answer.

For the time being, we will continue to treat this as a black box. We fertilize in a certain way and we end up with little or no algae. We are not sure exactly why no algae is the result.

The focus seems to be on NH4 as triggering algae spores to germinate. In my experience, I have seen algae blooms when something happens that interferes with my plants' steady growth. So, for example, one time I ran out of CO2 and didn't notice for a few days. This impacted my plants' growth. As a result, uptake of NH4 dropped presumably thereby increasing its presence in the water column. If the hypothesis is correct, this caused the algae spores to germinate. Hence, my algae bloom.

This is all conjecture, of course.