pop considers: Bacteria in the Freshwater Aquarium
Bacteria in the Freshwater Aquarium states “Autotrophic bacteria synthesize their own food, and they require oxygen so they are termed aerobic. Some do this via photosynthesis using sunlight, oxygen and water. Others use chemosynthesis, a process whereby they manufacture carbohydrates from carbon dioxide (CO2) and water using chemical nutrients rather than sunlight as the energy source.”
Do these autotrophic (aerobic) bacteria that require oxygen also produce carbon dioxide in the process sometimes referred to as aerobic respiration?
If this is correct the nitrifying bacteria in a cycled aquarium reloads carbon dioxide into the water Column.
What happens when the water column is in a state of oxygen deprivation will the autotrophic bacteria reverse the process and stop production of nitrates and begin converting nitrates to nitrites to ammonia or would the lack of oxygen cause the bacteria colonies to shut down?
the whole tank crashes.
the nitrates->nitrItes->nitrogen gas usually requires a low oxygen environment only found in the substate. Not in the water column itself.
the nitrates->nitrItes->ammonia also in the subatrate when a deep sand bed (DSB) is malfunctioning. Not in the water column
the Natrual Nitrate reduction(NNR) through bacteria is a big thing in marine systems up to 4-5 years ago. After several years of being recommended by everyone with all kinds of operational "secrets" to keep it going, some experienced and expert systems started crashing after 5 years or so of operations. Since then algae system usually in some kind of refugium have returned to various discussions.
In any event reducing nitrates with low oxygen bacteria leads to cyano bacteria problems.
While your concern is valid, it actually just points to using plant life to reduce nitrates instead of low oxygen methods. At least with plants consume carbon dioxide and return oxygen. Not to mention using ammonia/nitrates as well as phosphates.
I had not thought of reducing nitrates with low oxygen bacteria, so that works??
I was thinking just the opposite using highly oxygenated water column to eliminate ammonia before the nitrogen cycle begins. I guess this idea needs more work.
I wish you had addressed the aspect carbon dioxide production through the nitrogen cycle which is what interests me the most right now. Don’t plants release carbon dioxide through respiration also.
Similiar to what a nitrate reducer does only in that case in a low flow long tube environment sometimes helped with sulphur.
In the water column some dose vodka to encourage the bacteria as well. In that case it is very low amounts of vodka and overdosing can crash the entire system.
can't say anything about co2 but here is an interesting article on the process. My quick scanning did not reveal any co2 in there. but that doesn't mean there isn't.
Aquarium Chemistry: The Nitrogen Cycle: New Developments and New Prospects — Advanced Aquarist | Aquarist Magazine and Blog
I also found another reference that does mention co2 and also discussed denitrators and the chemical reactions
Aquarium Chemistry: Nitrate in the Reef Aquarium — Advanced Aquarist | Aquarist Magazine and Blog
I think that the idea of oxygen depletion in the tank is not a concern. Consider a tank loaded with plants and fish, the fish survive quite nicely overnight even though the plants have switched their process to respiration. I don't know how long it would take for the fish to deplete the O2 to a point where it would be a concern.
Supplying O2 to a tank would not be a cool idea. I can think of many safety concerns over someone tinkering with an O2 injection system. Easier just to add plants to suck up the ammonia before the bacteria do, they do that anywhere from 4 times faster to 50 times faster anyway.
And I thought that I over-thought things.
But IME what happens is the tank becomes a net consumer of co2 and producer of oxygen each 24 hour period.
In my old 55g marine tank I had a ph of 7.6 or lower. And basically constant but that also was the lowest reading with the test kit. The addition of marco algae resulted in a ph just before lights out of 8.4-8.8 (api high range test kit) indicating low co2. With low alk the ph dropped to 7.9 just before light on.
So what happened is that with the addition of the macros the lowest pH was much higher the highest pH before the addition of the macros.
So to me that indicates the plants had effectively reduced the co2 and raised the oxygen even though they respirate co2 at night.
My FW planted tanks even with peat moss in the substrate all have a pH of over 8.4. Yet fish "needing" lower values thrive and live for years.
Those articles on bacteria were very interesting mind telling me what search terms you used to pull them up?? Also macro algae generate carbon dioxide / oxygen during its life’s process so would it not be true that macro algae would as well be net producer of oxygen & carbon dioxide. This leads me to think about the exchange of carbon dioxide for oxygen is it one molecule of oxygen for one molecule of carbon dioxide or is there a ratio of (X) O2 for (1)CO2 molecule. If more molecules of O2 are produced for every molecule of CO2 consumed would explain the net carbon dioxide consumption. I need to think about this for a while thanks for the input.
Your point is very interesting way to think about life’s processes in the aquarium and I can only agree with your statement. It is funny how most folks here automatically think injecting CO2 or injecting O2 as the way to accomplish increases in O2 or CO2.
Just to let you all know iam a plastic plant man, with a lot of bubbles in my tank.
I like the way you have talked about this subject I have learned two new words macro algae and ontogeny
It's actually not a liguid CO2 as liquid CO2 is cyrogenic and a little bit cold to be adding to our aquariums.
But there are liquid suppliments like Excel that provide carbon for plants in a low carbon dioxide environment. That may be what you are thinking of.
Although the reduction of nitrates through plant action actually returns alk (carbonate?) in the same amount it was used up by the bacteria reducing wastes to nitrate, I have heard that in a low CO2 environment, plants would get carbon from carbonate. So that kH may be reduced. But that's just what I hear. In my tank with a plain sacn substrate, I noticed a marked increase in kh over years. With peat moss in the substrate kh remained level for 2-3 years.
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