how to balance co2 and oxygen

[nilesh7318]

i am having a confusion about the amount of co2 and the amount of oxygen in the tank. how do you balance both of them so that fish have oxygen to breath and plants have enough co2. a properly cycled tank does not require a air pump to create bubbles in tank so that it provides oxygen for the fish ( this is what they say in all forums and in the articles, only proper filtration is okay). then why do we have to provide plants with co2 supply from external sources. why is the co2 not generated inside the tank naturally.

 

[phin]

The 'air molecules' (N2, O2, CO2) around the tank will diffuse into the water and achieve equilibrium between the composition of the water and air. Diffusion occurs at the surface, whether that surface is the 'top' of your water or the surface between your tank's water and an air bubble. Filters generate movement at the surface to promote efficient & complete diffusion.

The air we breathe is ~78% nitrogen, ~21% oxygen, and less than one half of one percent carbon dioxide. Sufficient amounts of oxygen diffuse into your tank's water with appropriate surface agitation. Sufficient amounts of carbon dioxide also diffuse into your tank for plants to survive, but their growth will be limited.

Your plants growth is limited by the availability of nutrients, amount of light, and amount of carbon available. If you have $300 lights, and dose all nutrients sufficiently, but don't add a carbon source, your plants will be limited to the carbon available.

If you want to maximize your plants' growth you need to increase the amount of carbon available. CO2 injection is one way to do that. Using another carbon source, like Flourish Excel is another. When you inject CO2, it needs to be injected at a rate faster than it can diffuse into, and achieve equilibrium with, the air.

To address your question on why CO2 is not generated inside the tank naturally, it is, but not at amounts that would provide your plants with the extra carbon they need. In fact, your plants put CO2 into the water during the lights-out (respiration) period.

Hope this makes sense. Maybe someone can clarify my explination.

 

[meegosh]

Simply put, we inject CO2 into planted tanks to make photosynthesis happen extremely fast. We shoot lots of light at it, give it lots of nutrients via ferts and the CO2 has to be there to balance it all out. Typically a tank has a CO2 level around 7ppm without any injecting. The heavily planted/high tech tanks you see on here usually have CO2 levels between 25-30ppm.

Properly filtered tanks do not need any air bubblers because the filter agitates the surface enough and provides oxygen.

 

[phin]

that was probably a better way to say it.

 

[meegosh]

I'm a simple man. LOL

Yours was a lot more detailed! I didn't see your post until after I typed mine up. Sorry for stealing your thunder.

 

[phin]

no thinder stolen. I thought it was a ramblin mess

 

[nilesh7318]

The 'air molecules' (N2, O2, CO2) around the tank will diffuse into the water and achieve equilibrium between the composition of the water and air. Diffusion occurs at the surface, whether that surface is the 'top' of your water or the surface between your tank's water and an air bubble. Filters generate movement at the surface to promote efficient & complete diffusion.

The air we breathe is ~78% nitrogen, ~21% oxygen, and less than one half of one percent carbon dioxide. Sufficient amounts of oxygen diffuse into your tank's water with appropriate surface agitation. Sufficient amounts of carbon dioxide also diffuse into your tank for plants to survive, but their growth will be limited.

Your plants growth is limited by the availability of nutrients, amount of light, and amount of carbon available. If you have $300 lights, and dose all nutrients sufficiently, but don't add a carbon source, your plants will be limited to the carbon available.

If you want to maximize your plants' growth you need to increase the amount of carbon available. CO2 injection is one way to do that. Using another carbon source, like Flourish Excel is another. When you inject CO2, it needs to be injected at a rate faster than it can diffuse into, and achieve equilibrium with, the air.

To address your question on why CO2 is not generated inside the tank naturally, it is, but not at amounts that would provide your plants with the extra carbon they need. In fact, your plants put CO2 into the water during the lights-out (respiration) period.

Hope this makes sense. Maybe someone can clarify my explination.

very much thanks for your reply. seems you guys have done a lots of research. but still i would like to clarify some things,
1. when the fish breath oxygen, do they exhale out co2. does this co2 remain in the tank in dissolved state so that the plant can use them.
2. can you clarify this statement in your answer "When you inject CO2, it needs to be injected at a rate faster than it can diffuse into, and achieve equilibrium with, the air."

thanks again for helping me understand the theory.

 

[phin]

very much thanks for your reply. seems you guys have done a lots of research. but still i would like to clarify some things,
1. when the fish breath oxygen, do they exhale out co2. does this co2 remain in the tank in dissolved state so that the plant can use them.
2. can you clarify this statement in your answer "When you inject CO2, it needs to be injected at a rate faster than it can diffuse into, and achieve equilibrium with, the air."

thanks again for helping me understand the theory.

1. Yes. Cellular respiration in fish occurs the same way as cellular respiration in all other animals. The CO2 will remain in the tank and be available for plants to use, but will diffuse into the air eventually, achieving equilibrium with the air.

2. The CO2 concentration in your tank will constantly be attempting to achieve equilibrium with the air around the water. CO2 can only diffuse into the air so quickly, so if you inject CO2 faster than it can diffuse into the air and achieve equilibrium, you will have a higher concentration of CO2 in your tank than you would have without CO2 injection.

 

[nilesh7318]

thanks for the reply it clears all doubts.