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[APD] substrate ammonia, competition

Robert T Ricketts wrote:
> I have no idea what the situation would be for soil
> substrates which were
> not pre-soaked, or for other significant organic component substrates.

I agree with Robert that you won't generally see ammonia being produced
in the substrate because of nitrate in the water irrespective of whether
the substrate is organic or not. You will see ammonia leaching out
during the first month or so if you use a fertile organic soil such as
earthworm castings. Below the surface there is not enough oxygen and you
can get anaerobic bacteria reducing nitrate & nitrite to ammonia. This
nitrogen is originating from decomposition of material in the soil,
rather than from nitrate in the overlying water.

IMHO, a non-fertile organic mixture such as peat & subsoil won't have
enough labile organic matter to be a problem. In such a case, nitrate
from the water could be diffusing into the anaerobic region and being
reduced but at the same time, ammonia is diffusing back out, its also
being oxidized back to nitrate as it penetrates back into the oxygen
rich environment of the aquarium water.

In my current tanks, I'm using topsoil & subsoil mixed with a large
amount of peat. I bleach treat the tanks prior to setup and bleach all
equipment and use the 5% bleach treatment for plants. This kills
filament algae. I don't have problems with filament algae or green water
at all. There is usually a heavy growth of brown algae (diatoms) for the
first month or so however this is excellent snail food and if you have a
large snail population from the start, its not a problem either.

>From my experience I would agree that ammonia levels around 0.1 ppm lead
to green water blooms. I can't say definitely, based on my experience
alone, if lesser concentrations of ammonia (0.01 - 0.05) might encourage
Oedogonium. Its definitely worth considering.

I read Tom's comments about macrophytes competing with algae by
consuming ammonia and his suggestion that plants keep algae growth rates
down by keeping the ammonia levels down. I'm sure this is the case for
unicellular algae. I think its a good hypothesis for macrophyte &
filament algae competition but I think there are also other factors
helping the macrophytes too. In the case of Oedogonium, when you have
vigorous macrophyte growth, you can get relatively algae free leaves and
you can prune off the affected leaves. The Oedogonium is still present
in the aquarium but the combination of algae eaters and manual removal
keep the algae from covering everything. Another way that macrophytes
compete is by growing so fast that they block the light from the lower
levels and the algae there simply slows down.

Can Oedogonium, Cladophora or Spirogyra utilize nitrate nitrogen?

I tried to find an answer to this with Google; I did discover that
Cladophora vagabunda (a marine species) can store nitrate so at least
some species can utilize it, perhaps with lower efficiency. See

A Canadian study of algae in the Great Lakes shows a correlation with
SRP (soluble reactive phosphorus), and the presence of algae.
Nitrate/nitrite is on the increase however the algae are decreasing. It
doesn't shed much light on these questions other than to illustrate
concentrations of SRP, total phosphorus & nitrate where algae become

This suggests to me that with total phosphorus above 0.01 ppm or SRP
above 0.001 ppm that we can expect algae to be able to grow. It also
seems to suggest that algae do not flourish in situations where nitrate
is as high as 0.5 ppm when phosphates are kept low. I expect that we
can't expect to keep SRP below 0.001 in an aquarium so any algae that's
present is going to grow. To me that suggests that with conditions
conducive to healthy macrophyte growth, we can expect all kinds of
filament algae to be able to flourish. Ergo the best way to prevent a
problem with Oedogonium species and Cladophora species is to prevent
their introduction into the aquarium. If you don't do that, then you
need to have rapid growth of fast growing species and algae consumers
together with regular maintenance. Aquarium systems designed for very
low maintenance or for slow growing species can expect to have problems
with filament algae if they are present.

I think its worth noting that the way Tom B & I do planted aquariums are
radically different.


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