Art_Giacosa

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?

alexperez

IMHO I believe the reasons behind these methods are that the plants are no longer limited by any nutrients. And as long as the plants are growing the algae is kept at bay. Not very scientific, but my experience (see below) from the last 2 years have let me to believe this.



When I started keeping planted tanks, I read about the Sears and Colin paper about limiting Phosphates to stop algae growth. We’ll I tried that for a few months and always had BBA and fuzz algae. I kept the NO3 at about 10ppm and the PO4 below .5 ppm. While trying this method I got a bad PO4 test kit that was giving me high readings. We’ll I dosed at higher levels of PO4 (still thinking I was at .5 ppm) and the algae was getting less and less. My LFS in Arkansas tested my water and confirmed that my PO4 was over 2ppm. I got me another PO4 test Kit (La Motte) and Once again started the .5ppm Dosing and then the algae once again started appearing. I had to move to South Carolina so the tank was torn down.



In South Carolina I set everything up again and by now I had read about the EI method. So I started using it, and it working nicely. I had good plant growth and very little algae. I test almost daily (I Like to do it). And got a hold of a Bad NO3 test kit and instead of keeping up with the EI method, I believed the test kit more and so I dosed less NO3 than I should have. We’ll once again the algae came back. Once I figured that the NO# test kit Was bad. I gave up and bought all La Motte kits.
Once I started to dose and keep the NO3 at about 20ppm and the PO4 at about 2ppm the algae Once again stopped growing. We’ll it was Time to move again so I had to tear down the tank once more.




I set up the tank in Florida and everything was going great nice plant growth and no algae (EI Method). I now tested only once or twice a week and just dosed .5 tsb of KNO3 and 1.5 ppm of PO4 every other day. The test kits showed an average of about 20-30 ppm KNO3 and PO4 was always above 2ppm.
I recently had a mishap in the tank. After a water change for some yet unknown reason I lost about 70% of the Fish and about 50% of the plants. The plants that where left had stopped growing. And in a one week period I started seeing algae growing again. About 2 weeks after the mishap All the old and new plants where growing nicely again and the Algae stopped growing.



So from the above experience I concluded that any time the plants stop growing. Due to Lack of nutrients or for some other reason algae will quickly appear. Thats why the methods work they keep the nutrient levels that the plants need.

defdac

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?

Art_Giacosa

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?

Art_Giacosa

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.

S

Art_Giacosa

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

TWood

I'll hazard a guess just to keep this ball rolling.

I'll propose that the higher oxygen levels in a tank where the plants are doing well acts to suppress algae. How? Um, maybe the algae is so small that it gets oxidized? That is, the oxygen molecules tear it apart?

Someone like TBarr will probably come along and say "No, I've tested tanks with algae and no algae and both had the same oxygen level." If, so, then that theory is kaput, but I'd be interested in knowing if the correlation was studied.

TW

Art_Giacosa

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.

TWood

Hey Art,

No, not familiar with any of that. I just pulled this out of my, um, made it up out of thin air.

TW