# Healthy plants=O2=healthier plants=more O2=.......



## Pterogho (Feb 8, 2004)

In general, any aquarium is a mere interpretation of nature. 
But in one vital way every tank copies both the wild and the world of Man, -in the constant battle over limited resources.

Now! Let's instigate a war.
Take a water-proof container, possibly with at least one see-through side, and fill it with water.
After some time you're likely to feel pretty bored with this arrangement, so you add some life in the form of fish, plants or other, and so the fight for oxygen is on.!!!

The vital function of O2 is not up for discussion.
In our tanks there is a constant "exploitation" between on one side the O2-producers , and on the other side the O2-consumers.
To the O2-consumers belong primarially the plants during the dark hours, and all the micro-organisms.
The portion of O2 used by the fish is on the contrary relative low.
In this scenario, only the plants are able to exist at a self-sustaining state.
Still, observed from a higher point of wiev, the O2-consumers all give out CO2, so in a sense they are also self-sustaining by delivering one of the most crucial elements in the process of O2-producing in a planted tank .

During the day, the assimilation of the plants will steadily increase the level of O2 in the water, reaching the maximum during the evening, secondly can O2 be absorbed from the athmosphere by a unsettlement of the surface, but athmospheric air is a compound of which O2 does NOT form the greater part.
On the contrary, a high assimilation-process of plants can lead to a saturation of more than a 100% of pure O2, and this while the surface is kept completly calm, and so keeping the loss of vital CO2 at a minimum.
The O2-requirement of the organisms in an aquarium increases with a rise in temperature.On the other hand, is the O2 saturation-point of the water also temperature-dependant. It goes something like this:
At 20 C approx. 9,4 mg/l, at 25 C - 8,6 mg/l and at 30 C -8,0 mg/l.
The cooler the water, the more O2 it can hold.

Christel Kasselmann , author of 'Aquarienpflantzen, DATZ-Atlanten, ISBN 3-8001-7298-4', reports of a crystal-clear pond with a thick growth Elodea canandensis, in which tests proved an O2-saturation of 198%. 
Such an over-saturation of O2 is, though, not likely to happen in an aquarium, but it demonstrates very well, that the O2-producing capacity of plants, is well beyond the consumption by the various aquatic organisms, and the emission-rate through the surface.

The generally forgotten knowledge in regard to plants, is that with an increasing O2-level in the water, the plants also perform a higher breathing-intensity, and hence a higher metabolism, meaning a higher consumption of nutrients, including nitrates.
Think of this; plants, like f.ex. Anubias and Bolbitis, that are known for a guite slow growth-rate, inhabit quite fast-moving, O2-rich waters in the wild. Had they been just as slow growing out there, they wouldn't stand much of a chance in the natural competition.
Think of how easily these plants succumb to algae in many tanks.

It may sound a little less financially liable with such hungry plants in your tank, -like they would constantly be crying out to you for fertilizers.
But according to tests performed by Christel Kasselmann and others, over several years, this is not indisputably the case, on the other hand, a complete vanguishment of blue-green algae was observed.
The results were obvious, but the underlying processes were not, though.
Still, isn't a tankfull of healthy strong-growing plants a wonderfull way of pampering your fish?
---Qouting Mr. Amano Takashi: "A beautifull plant make a beautifull fish."
Another, in no way secondary, benefit of a high O2-level is the stronger multiplifation-rate of the nitrifying, and other aerobic, bacteria existing in every up-and-running tank, leading to a faster oxidification of debris and poisinous substances into harmless ones.

Some decades ago, it was the generel believe, that planted tanks should only be allowed a minimum of O2-content, as an oxidation of some nutrients could make these un-obtainable to the plants.
Fact is, that no clinical tests have proven this to be a real issue.
Some would even argument that too much O2 would leave less room for CO2 in the water, which is absolutely nonsense. O2 and CO2 does not replace each other
These days, though, there is no reason to deny any aqauaristic set-up the benefits of water over-saturated with O2, 'cause now any seriuos fertilizer on the market contain Chelators, that bind oxidated nutrients.


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