# Why is it true that healthy plants prevent algae growth?



## MiamiAG (Jan 13, 2004)

I was away from the hobby for a few years. While I was away, Tom seems to have come up with a way (better way?) to limit algae growth and increase plant health. [Gees Tom! Where were you 15 years ago when I was growing algae forests]

My questions is why does Tom's "Estimative Method" work?


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## plantbrain (Jan 23, 2004)

I just was not able to type back then nor owed a computer
I had a some moderate algae issues, not like many folks though.
I was not happy with the aqauscape or the slight algae preseance though. 

I think there are several reasons for low algae at moderate nutrients.


PR may cause some of algae basal cells to release on plant leaves.

Water changes always seem to help. Removes many epiphytic algae and any that are floating around.

We scrub, prune old leaves that get infected.

We add herbivores. 

Algae spores may not have any signal like NH4 presence telling them to grow(plants remove all the NH4 when they are healthy!).

High O2 levels may activate bacteria in the substrate that suppress algal spores that are generally present in the substrate much like a seed bank/reservior.

The nutrient levels are great for plants, they out pace and out grow algae when feed a stable diet, algae are better able to deal with dramtic changes while it takes much more time for plants to get established.

This issue has not been explore much in the literature, mainly phytoplankton vs macrophytes , seldom periphyton/epiphytes vs macrophytes in the context that is useful for planted aquarist.

Some suggest allelopathy, but all 300 species of plants elicit the same response? What is the likelyhood that all 300 species have the same chemical and effect? Extremely small. 

These are a few ideas.
Observations are fairly clear, why this occurs is not so clear. 
I have suggested a few ideas.

It has to be something general.
I think it has a lot to do with algae's signaling to bloom or stay put till things get ripe again like with NH4. 

Everything I've done with NH4 tells me it's the problem in natural ecosystems and in planted tanks, SW or FW. 
Many bothersome algae bloom readily with NH4 additions. 
But they don't if you add NO3+the other nutrients.
You can try this by adding more and more fish to a thriving healthy tank.
Once you pass by the rate of NH4 uptake by those plants, you provide a ripe place for algae to grow. You can add everything else and not get a response. 

Plants and algae occupy different ecological habitats also. A small amount of NH4 means a lot to the algae vs the plant. 

Regards, 
Tom Barr


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## MiamiAG (Jan 13, 2004)

plantbrain said:


> I just was not able to type back then nor owed a computer


Ahemm. What are you saying Tom??


plantbrain said:


> PR may cause some of algae basal cells to release on plant leaves.


What does PR mean?



plantbrain said:


> Algae spores may not have any signal like NH4 presence telling them to grow(plants remove all the NH4 when they are healthy!).
> 
> High O2 levels may activate bacteria in the substrate that suppress algal spores that are generally present in the substrate much like a seed bank/reservior.


This would imply some sort of genetic mechanism in algae?



plantbrain said:


> Plants and algae occupy different ecological habitats also. A small amount of NH4 means a lot to the algae vs the plant.


Thinking about it differently, you are suggesting the algae do not reduce nitrate as readily as plants do and hence suffer from a nitrogen deficiency? I have no basis to disagree with you that there may be some genetic trigger to the presence of NH4. I just find it more plausible that it has something to do with nitrogen competition.

What do you think?


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