pop's opinon: Oxygen and it's diffusion
How did ole school fish keepers ever succeed with notions of sunken pirate ships, bubbly treasure chests and plastic plants with wonderful air bubbles? They don’t exist anymore except when one remembers the ole times.
Now days the new school of fish keeping is introducing new ways to view fish keeping based on timely presumptions of science. This new school of fish keeping has introduced me to the concepts of aquascaping … re-creating a natural environment, the importance of monitoring water parameters for water quality and the nitrogen cycle.
I have read many posts about necessity of cycling aquariums and the importance of helpful bacteria that convert ammonia through processes into nitrate. The pillars of new school fish keeping also pointed me to the importance of a well planted aquarium including floating plants. It appears when there are enough live plants then one can become less concerned about the earlier dictates. In fact when enough plants are present in the aquarium they consume the ammonia so the cycling process and the nitrogen cycle become almost meaningless as will the necessity of checking water quality. The planted aquarium has saved us all; there isn’t even a need to worry about aeration of the water column.
Time honored notions like ph and temperature are still valued but the pleasing hum of the air pump and soft sounds of air bubbles aerating the water column is no longer desired. Aeration is not the way to achieve a balanced system. The current idea views aeration in a negative manner citing the loss of carbon dioxide that the plants need for photosynthesis. Besides there is more than enough oxygen in the water and it is continually being replenished.
Why should I think about oxygen and how oxygen is replenished when no one else appears to be concerned?
We all know that water is made up of two hydrogen molecules and one oxygen molecule (H2O) and that there are two ways of adding oxygen to the water column.
It is common knowledge there is gaseous exchange that naturally occurs between water and oxygen where atmosphere interfaces with water, also it is common knowledge that aquatic plants create during photosynthesis waste by-product oxygen.
Some terms: When oxygen is added to the water column it is referred to as Dissolved Oxygen (DO). The process of oxygen dissolving in water is sometimes thought of as diffusion. The amount of dissolved oxygen in the water column is known as saturation.
Since water must follow natural process, it doesn’t matter if the water is in the form of river, lake or water column in my aquarium solutes always finds a state of balance. What this means is any concentration will attempt to move toward areas of less concentration bringing balance to the solute. This process also applies to how oxygen is replenished at the surface of the water column. One way to think about this is oxygen molecules are constantly entering and leaving the water surface at all times. The natural attraction of oxygen molecule to water is determined by the DO saturation. This means that water with low dissolved oxygen saturation is more attractive to oxygen molecule than water with high dissolved oxygen saturation. Oxygen’s affinity towards water is also defined by the concentration of oxygen in the atmosphere in contact with the water column. The difference between atmosphere concentration of oxygen and saturation levels of dissolved oxygen determines the rate oxygen will diffuse into the water column.
There are other considerations other than oxygen concentration that contribute to saturation levels of water. One of these factors is the surface area of water that is in contact with the atmosphere and ambient temperature.
Cool waters have greater levels of DO saturation than warm water.
There are many ways to talk about oxygen diffusion into water and we all can agree that
a sufficient level of dissolved oxygen is the most fundamental requirement of all aerobic aquatic organisms, and maintaining a high dissolved oxygen level is an essential of fish-keeping.
Note: I am using the notion of osmosis to discuss how oxygen enters the water column, there is not any real science that supports the way osmosis model is used in this methodology.
but we do have to remember that in the night plants consume oxygen and there for leaving an accumulation in carbon dioxide for the plants to eat as the light returns in the morning
meaning that aeration is very good if used right and at a very slow rate
now brain storming here a bit but what if
we had a timer on our air pump's and having no air for two hours before light to magnify this carbon dioxide build up
this must be a very stable setup and also maybe even have it off for a few hours in the day too
I love oxygen.
If you are considering planted tanks having CO2 diffusion, then that is normally turned off with the lights (otherwise it is being wasted). Some do suggest aeration at night in these tanks, since the planting itself is often quite different so the normal balances are not the same.
The CO2 in a natural planted tank rebuilds during darkness, but this is never going to be catastrophic unless again you have some abnormality occur. Tests have suggested that the CO2 level that rebuilds is most likely to be exhausted by the plants after just a few hours of light (photosynthesis). This is the reason behind to so-called "siesta" approach to promote more plant growth without CO2 diffusion.
Another point is that Oxygen increases can be detrimental to plants. In high oxygen environments, plants have difficulty assimilating nutrients. A small dissolved oxygen content is required for plants. Higher dissolved oxygen cause nutrients such as iron to bind with the oxygen, becoming too large for plants to assimilate. High oxygen levels also inhibit other nutrient uptake.
Good Morning Byron and other fish keepers:
I was surprised to read your post this morning. What you pointed out sounds very reasonable. We all understand that too much of anything can be an unpleasant experience. Thanks for the information about high oxygen concentrations being bad for plants (gives one some food for thought).
Your point about ‘Higher dissolved oxygen cause nutrients such as iron to bind with the oxygen’ leaves me wondering are you thinking about iron oxidation, you know rust.
Would excessive dissolved oxygen have an effect on bacterial oxidation as well altering the micro-ecology’s food chain?
I guess that I have been clarified right into another subject.
Have a good day,
One of the detrimental effects of undergravel filters in planted tanks is the constant circulation of oxygen-rich water through the substrate [much faster than what normally occurs]. Micronutrients like iron stay locked up in their oxide precipitates, which plants cannot use.
I also came across some data with respect to the issue of oxygen depletion at night. Oxygen like CO2 diffuses much more slowly in water than in air, some 10,000 times more slowly. Oxygen therefore has difficult escaping from the plant, and this inhibits photosynthesis by stimulating photorespiration, a wasteful process that releases fixed CO2. This can reduce photosynthetic efficiency by 20-25%.
Walstad mentions that while plants do respire continually, they prefer using their stored oxygen for this. Some 70% of the plant's interior is made up of lacunae, which are basically large gas chambers where oxygen is stored; this provides most of the oxygen for plant respiration. Oxygen is also released through the roots.
This is great stuff she even uses words that are descriptive. Just think about the bacteria and what they do. You have the Autotrophic that nitrify ammonia and the other types Heterotrophic that process organic nitrogen (from the atmosphere), organic matter and mineralize minerals in the water column and they are completing for surface area to colonize and dissolved oxygen. Which bacteria prefer oxygen rich waters are the autotrophic bacteria. Perhaps the Heterotrophic that processes iron molecules iron into plant useable mineralized version will not exist in oxygen rich waters (since this occurs only when top soil / clay is used as substrate). Let’s think about how the food chain works in an micro ecology and consider the Autotrophic that process nitrogen reduction as an example. First the ammonia is converted by bacteria to nitrate and the next phase of bacteria use the processed nitrate as energy source with the by product of nitrate which is then removed by water changes. This is a progressive process in which the by-product of energy production of one life form provides the energy source for another form. In this type of methodology mandates that at every level of consumption be rooted to the output of the life form supporting it. Therefore Heterotrophic like low levels of dissolved oxygen and can not live in highly oxygenated waters.
There is something missing in the second quote but this is what I think is happening.
“Oxygen therefore has difficult escaping from the plant, and this inhibits photosynthesis by stimulating photorespiration, a wasteful process that releases fixed CO2”. This is a logical leap ……….. all substances dissolved in water migrate from highly saturated area’s to less saturated areas and this principle applies to plants. When the water column becomes excessively saturated with dissolved oxygen the migration of DO produced by plants is restricted forcing photosynthesis into a shut down mode just like they do at night and release carbon dioxide. In this view of natural processes there always is a limiting element that controls the process and in this case the limiting element is excessive dissolved oxygen.
I have also read that plants produce great amounts of DO much more than plants use for respiration. Miss Dianne is one hot thinker where would we be without her insights.
Note: No one should consider the view presented as being nothing more than a shot in the dark, a guess about how natural process function. Each fish keeper must decide for themselves the correct understanding, read the article bacteria in freshwater in article section.
You’all can’t catch the pumpernickel possum
he done caught the midnight ride out of town
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