Airstones & Necessity To Add Carbon While Lights Are On

Okay, so I have a few things I want to say and a few questions. The first thing is that I recently got an ayirstone in my heavily planted, no CO2, 20 long due to an apparent water flow dead zone on the right side of my tank. Since I am using liquid carbon to feed my plants' calvin cycle (for now) I don't have to worry about the off-gassing of co2 during photosynthesis.

Now I want to talk about aquarium CO2 in relation to photosynthesis. In photosynthesis co2 is NOT used during the light-dependent phase, which uses light energy and converts it to NADPH & powers the creation of ATP. CO2 is used during the calvin cycle (light-independent) phase of photosynthesis to produce a carbohydrate called g3p, which is used to create sugars and build the plant up. Keeping that in mind, why do people say you should only let CO2 run while the aquarium lights are on? Is it because the calvin cycle takes place immediately after the light-dependent phase(not a rhetorical question, I don't know how quickly it occurs after light-dependent phase)? And how does liquid carbon help plants grow? In the calvin cycle, the chemical reaction occurs by bonding CO2 with RuBP, can the plant really substitute some sort of artificial carbon-based compound for CO2? I just really want to make sure I'm not wasting any money buying liquid CO2 or an extra timer to turn on the bubbler at night only when I finally do start injecting co2, if there is no scientific evidence that they will help.

 

Here is my attempt at a scientific answer: do you know if plants take up CO2 during the photoperiod and only fixate it at night when the lights are off to produce new growth? That is the only thing that makes sense to me.

Here is my practical answer: If you ever measure the CO2 in a planted aquarium you will see levels will drop down during the photoperiod. In some cases the light is so bright that there is no CO2 in the water and this is where algae starts to take over. That is why people inject CO2, to keep a constant level during the photoperiod. Based on that evidence we assume plants use CO2 during the photoperiod. Liquid CO2 is glutarehyde which I guess eventually breaks down into carbon for plants. It does help. But it can also kill fish and certain plants if you are not careful. You aren't supposed to run an airstone at night if you are injecting CO2, you just close the valve.

 

Here is my attempt at a scientific answer: do you know if plants take up CO2 during the photoperiod and only fixate it at night when the lights are off to produce new growth? That is the only thing that makes sense to me.

Here is my practical answer: If you ever measure the CO2 in a planted aquarium you will see levels will drop down during the photoperiod. In some cases the light is so bright that there is no CO2 in the water and this is where algae starts to take over. That is why people inject CO2, to keep a constant level during the photoperiod. Based on that evidence we assume plants use CO2 during the photoperiod. Liquid CO2 is glutarehyde which I guess eventually breaks down into carbon for plants. It does help. But it can also kill fish and certain plants if you are not careful. You aren't supposed to run an airstone at night if you are injecting CO2, you just close the valve.

Let me correct you for that last part, at night when plants are no longer getting light for photosynthesis they release a decent amount of co2 and carbon levels will actually rise. I want my fish to have as much oxygen in the tank as possible when they are sleeping, considering it is the time of the day when they are barely moving at all, making it harder to absorb large amounts of oxygen in mediocrely oxygenated water.

Also, I understand that you do not leave the co2 system running at night and you close the valve, but when no light is present the plants will be releasing quite a bit of co2 anyway in heavily planted tanks through cellular respiration (despite it being commonly believed that animals use oxygen to produce co2, and plants use co2 to produce oxygen, plants also use oxygen to produce co2). This means in heavily planted tanks fully stocked and little or no surface agitation (what I have, high water levels + aquaclear doesn't do much for agitation) o2 levels will drop at night and co2 levels will rise while no light is present, so an airstone on at night providing high levels of oxygen will allow both the fish and the plants to do as much cellular respiration as they want/can.

Thank you for the rest of your advice!

 

If plants capture CO2 at night how would they also expel co2? I thought plants only used O2 at night and because they aren't producing any they take a dent on O2 levels. I am keeping right now a 10 gal filterless tank and with enough plants to support 9 Corydoras Pygmaeus and an Otocinclus. So far the fish haven't died at night lol.
Surface agitation from the filter output should be enough to keep O2 levels good enough at night.

I am not very informed on the scientific aspect of photosynthesis as you can see, but so far I haven't killed any fish in the making of my planted tanks, so I think I must be doing something right haha.

 

Dear DylanM ,

I cannot answer your question accurately but I can give you advice on what you should be doing from an advanced aquascaping point of view.

Ideally, you should be keeping the CO2 concentration in your water column steady through out the 24 hour cycle of your environment at 30 ppm. I personally keep mine at 40 ppm. You can have higher CO2 concentrations without any issues if your O2 concentrations are also kept high at all times. First you should fine adjust your CO2 injection according to the plants CO2 uptake throughout the photosynthetic period so that your ph stays stable. After you have achieved a stable ph and CO2 concentration for the photosynthetic period by fine adjusting the injection then you should fine adjust how much air you inject from your air pump at night to keep the ph stable also throughout the night. You will be injection CO2 and air both at the same time during the night. The air pump will be mimicking the plants photosynthetic activity by off gassing CO2 and adding O2 just enough to be at the same rates with your plants photosynthetic activity rates. Therefore you will be keeping the environment stable throughout the 24 hour cycle.

Please feel free to ask any further questions. I will be more than happy to help.

Happy Fish Keeping

 

If plants capture CO2 at night how would they also expel co2? I thought plants only used O2 at night and because they aren't producing any they take a dent on O2 levels. I am keeping right now a 10 gal filterless tank and with enough plants to support 9 Corydoras Pygmaeus and an Otocinclus. So far the fish haven't died at night lol.
Surface agitation from the filter output should be enough to keep O2 levels good enough at night.

I am not very informed on the scientific aspect of photosynthesis as you can see, but so far I haven't killed any fish in the making of my planted tanks, so I think I must be doing something right haha.

I understand, the airstone at night fish aspect of what I was saying was more out of paranoia. My main point is that plants apparently begin to use co2 in the calvin cycle almost immediately after they begin producing NADPH through the light-dependent aspect of photosynthesis (here is a to help you grasp the content and know what I am talking about a bit better) , which I learned after talking to my college bio major mother.
This means at night they are using up almost no co2 (still a little, considering we aren't living in the center of a black hole), but they are still using O2 and giving off CO2 through respiration. This can result in a lessening in plant growth due to a lower concentration of oxygen in the water at night, which makes it harder for the plants to perform cellular respiration to produce energy from the sugars made from photosynthesis during the day. So, a bubbler will give the plants more oxygen at night, allowing them to convert all of their sugar to energy at night, thus theoretically boosting their growth rate.

 

Dear DylanM ,

I cannot answer your question accurately but I can give you advice on what you should be doing from an advanced aquascaping point of view.

Ideally, you should be keeping the CO2 concentration in your water column steady through out the 24 hour cycle of your environment at 30 ppm. I personally keep mine at 40 ppm. You can have higher CO2 concentrations without any issues if your O2 concentrations are also kept high at all times. First you should fine adjust your CO2 injection according to the plants CO2 uptake throughout the photosynthetic period so that your ph stays stable. After you have achieved a stable ph and CO2 concentration for the photosynthetic period by fine adjusting the injection then you should fine adjust how much air you inject from your air pump at night to keep the ph stable also throughout the night. You will be injection CO2 and air both at the same time during the night. The air pump will be mimicking the plants photosynthetic activity by off gassing CO2 and adding O2 just enough to be at the same rates with your plants photosynthetic activity rates. Therefore you will be keeping the environment stable throughout the 24 hour cycle.

Please feel free to ask any further questions. I will be more than happy to help.

Happy Fish Keeping

One thing confused me, you said leave co2 injection on at night? "You will be injection CO2 and air both at the same time during the night." This will literally do nothing for the plants, considering they do not have enough light at night to produce a relevant amount of G3P. With the air bubbler on at high at night, along with the CO2 on, I can see no advantage, only wasted, off gassed CO2, and lower O2 concentration.

 

The air pump will be mimicking your plants as if it was the lighting ( photosynthetic ) period by off gassing CO2 and providing O2. But the air pump will be fine adjusted to your plants day time rate of CO2 intake. We do this to keep the concentrations stable. Which both plants and fish prefer and the algae spores hate The O2 concentrations are never low in this approach, on the contrary, they are at full saturation all through out the 24h cycle.

But again, this is the most ideal of approaches. Huge majority of aquascapers don't bother using this approach as it requires too much fine adjusting and stability. They just use the stop injecting at night and not aerate approach because the O2 build up from the photo period together with some surface agitation seems enough. You can not stop injecting and aerate at the same time. That would result in catastrophic fluctuations.

 

I am confused now and I wish my mom was also a bio major so I could ask all my questions but I agree with what KeeperOfASilentWorld said.

 

I am confused now and I wish my mom was also a bio major so I could ask all my questions but I agree with what KeeperOfASilentWorld said.

BeanFish Can you check out my stocking thread about my upcoming jungle scape? I would really appreciate your opinion

 

The air pump will be mimicking your plants as if it was the lighting ( photosynthetic ) period by off gassing CO2 and providing O2. But the air pump will be fine adjusted to your plants day time rate of CO2 intake. We do this to keep the concentrations stable. Which both plants and fish prefer and the algae spores hate The O2 concentrations are never low in this approach, on the contrary, they are at full saturation all through out the 24h cycle.

But again, this is the most ideal of approaches. Huge majority of aquascapers don't bother using this approach as it requires too much fine adjusting and stability. They just use the stop injecting at night and not aerate approach because the O2 build up from the photo period together with some surface agitation seems enough. You can not stop injecting and aerate at the same time. That would result in catastrophic fluctuations.

I'm pretty sure you can stop injecting and aerate, as the plants are actually removing added O2 and producing a generous amount of CO2 at night. If you can find the right pressure for your airstone to run at at night, that keeps the O2 and CO2 levels the same as they were during the day, you don't need to be injecting CO2 since the plants are already converting O2 to CO2 at around the same rate you are adding O2. This "only inject during the day and only aerate at night approach" is not achievable in a lightly planted, high tech tank, as there is not enough CO2 being produced by the small amount of plants to keep levels stable at night.

 

I'm pretty sure you can stop injecting and aerate, as the plants are actually removing added O2 and producing a generous amount of CO2 at night. If you can find the right pressure for your airstone to run at at night, that keeps the O2 and CO2 levels the same as they were during the day, you don't need to be injecting CO2 since the plants are already converting O2 to CO2 at around the same rate you are adding O2. This is not achievable in a lightly planted tank with injected co2, as there is not enough co2 being produced by the plants to keep levels stable at night.

The balance you are mentioning is not achievable. Maybe it would be achievable in a lab environment with zero surface agitation, no fish, no bacteria and only plants but not in an aquascape. There are too many variables. I think you will get a better sense once you start experimenting with them. The major goal here is to keep the ph stable.

 

The balance you are mentioning is not achievable. Maybe it would be achievable in a lab environment with zero surface agitation, no fish, no bacteria and only plants but not in an aquascape. There are too many variables. I think you will get a better sense once you start experimenting with them. The major goal here is to keep the ph stable.

I have found a very interesting post on another forum about running airstones at night and CO2 during the day in heavily planted aquariums. He found that O2 concentrations could drop 20 - 50%(3 - 7 ppm) during the night with no aeration in heavily planted aquariums, this. When running the airstone with high power at night this dropped quite a bit, with the change in O2 levels going from 14 ppm -> 7 ppm, to 14 ppm -> 8 or 9 ppm. Obviously a higher change in O2 concentrations could stress out the fish, and possibly cause issues with plants, so I have come to the conclusion that I will be running my airstone during the night only, and CO2 during the day only when I get my CO2 injection set up. If anyone has any reason why I couldn't be able to do this in an aquarium with a moderate KH level please let me know. Also, adding O2 at night can apparently help with pearling in the morning.

 

The calvin cycle happens pretty much immediately after the light dependent phase starts, if that was your original question?
Excel works by introducing carbon compound chains that are similar to what plants produce on their own, and they convert it to what they need, at least that's the gist of what seachem's website says. It works, but isn't as effective as injected CO2.

 

The calvin cycle happens pretty much immediately after the light dependent phase starts, if that was your original question?
Excel works by introducing carbon compound chains that are similar to what plants produce on their own, and they convert it to what they need, at least that's the gist of what seachem's website says. It works, but isn't as effective as injected CO2.

I know that now, and I use API CO2 booster along with seachem macro liquid ferts (potassium, nitrogen, & phosphorus). I have a medium-high light, a finnex planted+ 27/4 SE, so if I were to start injecting CO2 I'd have a full high tech planted tank! That would be awesome!

 

Here is a helpful video:

What I do is I keep my levels on the green threshold line all throughout the 24h period with zero fluctuations.
Hope it helps.

Here is another helpful video on CO2: