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[APD] RE: theory behind algae control

> If I understand it well, somehow the algae should be inhibited because the
> plants are growing actively. I am not denying this, as I can see the
> with my own eyes. But on the other hand, this clearly can not be nutrient
> competition, as the concentrations of all the important nutrients are
> and no algae problems occur as long as CO2, N, P, K and micro's are
> abundant. So, what could it be then?
> Roeland

They are in different niches, microphytes(algae) occupy a different habitat
than plants do. 
They have different needs. Actively growing plants do not make for a good
substrate to attach.
Actively growing plants use up all the NH4 produced within a system.
Actively growing plants produce large amounts of O2 and add a sustantial
amount of O2 to the substrate. Actively growing plants do not decay and
loose leaves that turn into growth losses and decayed matter that algae
will be able to use.
Algae can use dissolved organic forms of P and N, (DON, DOP) wereas most
submersed plants cannot. Large water changes will remove the organic
fraction that builds up.
But...... a healthy well balanced bacterial colony will help reduce the
DON/DOP and reminerilize the decayed matter. This takes perhaps 3-4 weeks
to occur. Once this occurs, the tank can get away with less water changes,
but it still helps to have the large water changes to keep anything from
running out(nutrients).

There are a number of theories about this issue in natural systems. Take
Florida lakes for example. These are far better models than say a lake in
WI that is very cold and freezes every winter, tend to be deep, have few
plants and onl;y a few months of the year. Florida lakes are shallow(most),
clear, full of plants and never freeze and generally much closer to
tropical conditions. This is obviously a much better model and these lakes
are well studied and there are a wide range of conditions and lakes types
for comparisions.

Lakes that get more nutrients added often will get more plant biomass, not
algae. Florida lakes have serious weed problems as the lakes have been
stabilized and the levels kept constant(eg Army Core).This favors the
The main competitive advantage in nature is generally light, not nutrients.
See Canfiled, Hoyer, Haller, Bowes and the IFAS web site for searches on
this topic. 
Allelopathy is sometimes suggested, but this has ___never__ been
demonstrated in any natural system in any research. But our systems are NOT
natural, yet many want to suggest natural systems are the best models for
growth and conditions for aquatic plants. Clearly, when speaking of
agriculture, natural wild corn growing out in nature is not going to yield
the best production. The same is true for horticultural plants in aquariums
or otherwise. 

We prune infected plants of algae, do water changes regularly, add high
densities of herbivores, scrape the glass free of algae, clean and export
nutrients, add CO2 which favors the plants higher growth rates at low light
intensities(our lighting is very low compared to natural sunlight), add
lots and lots of plant biomass from the start(this makes it hard for algae
to get a foothold), provide enough nutrients for the plants to keep
actively growing. We re set the tank's dominace often. 

So non CO2 tanks?
Less light, high plant density, herbivores, less loading, low NH4 levels
like a CO2 enriched system. This system is slower, light is less, dosing is
from the fish waste and some from the substrate initially and some Fe and
Mn over the longer term. But the differences are not great, both work for
many of the same reasons.

The lowest occurance of algae will be at low light(1.5-2w/gal), CO2
enriched, fast growing plants at high biomass density, well balanced
bacterial colony, good stable nutreient levels, lots of herbivores, regular
pruning and export of waste.  
I did not clean the front of the glass or see any visible algae for 6
months in a similar tank. 
There is no scientific debate over aquarium algae in FW planted tanks to
speak of, there is a a good deal in natural lake systems.

Tom Barr



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