Do I have enough co2. A closer look.

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Caliban07

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Carbon dioxide (co2) in earths atmosphere is around 400ppm and climbing. Most of our aquarium plants that end up in our tanks are grown in plant farms or factories around the world where they have access to this number or sometimes more if enriched further (hydroponics) so why do we expect our plants to accept a drop on average of around 395ppm carbon dioxide without some form of repercussion?

You would think that because the earths soil contains approximately three times that of the atmospheres carbon resources that plants would naturally take up their carbon requirements from their soil roots however, although this does happen where some plants are concerned the majority of their co2 requirements are taken in through the atmosphere via their leaves by a process called diffusion.

As soon as the plant is submerged in water it's access to co2 plummets dramatically. Why is this?

Co2 diffuses 10,000 times slower in water than in air.

Pure h2o at a temperature of 25 degrees Celsius and an atmospheric pressure of 1 bar will contain approximately 0.5ppm of co2. On average a typical aquarium will contain around 5-6ppm of co2 in doors. This can be increased by a number of means which we will go in to later.

Now we need to understand how plants respond to changes in co2 availability when placed under water.
One thing you may have noticed is how different some plants can look when grown emersed as opposed to submersed. Normally the whole leaf structure can look vastly different. Why do plants alter their leaves when placed underwater? One of the obstacles that plants must overcome is the leaf/water interface know as the prandtl boundary layer and it presents probably the greatest resistance to diffusion. This boundary layer surrounding the leaf is much thinner in submerged plants and the surface area of the leaf is often altered. The thinning of the membrane allows easier diffusion of gases through the leaf. Flow also helps this action. Turbulent flow generated at the leaf boundary layer improves the transfer of water containing co2 in to the leaf surface where it can be absorbed.

These new leaves will also have altered amounts of one of the most abundant enzymes on the planet called rubisco.
It is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants and other photosynthetic organisms to energy-rich molecules such as glucose and makes up around 50% of soluble leaf protein. Without it, photosynthesis would not be possible. But RuBisCO is pretty poor at its job. Some enzymes can carry out thousands of chemical reactions each second. However, RuBisCO is slow, being able to fix only 3-10 carbon dioxide molecules each second per molecule of enzyme. The reaction catalyzed by RuBisCO is the primary rate-limiting factor of the Calvin cycle during the day. Nevertheless, under most conditions, and when light is not otherwise limiting photosynthesis, the speed of RuBisCO responds positively to increasing carbon dioxide concentration.

Unfortunately However, approximately 25% of reactions by RuBisCO instead add oxygen creating a product that cannot be used within the Calvin cycle. This process reduces the efficiency of photosynthesis, potentially reducing photosynthetic output by 25%. This process is known as photorespiration. If the co2 availability is low enough such that o2 primarily enters the Calvin cycle the plant will waste away (melt) and die.

Plants in low co2 environments have leaves that contain lots of RuBisCO so that more co2 can be captured and entered in to the Calvin cycle. Plants in high co2 environments do not require as much RuBisCO because their is more co2 available and so greater chance of capturing the co2.
When plants are submerged they will often shed their old leaves for food and grow new leaves reflecting these alterations. This adaptation can take time and often results in algae outbreaks as old leaves are broken down.
Plants that go from low co2 to high co2 adapt much better than those that go from high co2 to low however, once the latter have adapted they can continue to grow healthily. These plants are more likely to be the 'low tech' plants such as Anubias and Crypts. Understanding how the plants adapt to co2 changes is important and highlights the need for patience.

How can we ensure we have enough co2?

In non injected co2 tanks having more fish equals more bioload which equals more food which equals more waste which equals more microorganisms with ultimately equals more co2 via respiration. Having a generously stocked tank can increase co2 levels.

Some water supplies contain healthy amounts of co2 depending on the source and so frequent water changes can increase co2 availability.

It is important to understand that plants can survive in non injected co2 environments but this is not always the case.

What factors impact my success in planted tanks with regards to co2?

If I am injecting co2 in to the water column I immediately have a better chance at growing a wider variety of aquatic plants but we must look at these points below to determine our chances of success even with additional co2.

Size of aquarium.

Much more difficult to keep co2 in solution long enough for plants to obtain enough as their is more likely to be a larger water space to plant ratio and thus co2 is wasted

Plant mass

More plants will require more co2.

Plants species

Different plants have different co2 requirements. Therefore their uptake rates can differ dramatically. Most stem plants for example are aquatic weeds that take up co2 quickly.

Light intensity

Light intensity drives co2 uptake and so the higher your lighting levels the more likely co2 will become depleted quickly. Therefore a solution in lower co2 environments can be to lower the light intensity and reduce the plants demand for co2.

Flow pattern/strength

As discussed above flow cannot be underestimated. Do you have enough and is it distributed correctly?

Temperature

Higher temps will hold less co2.

Surfaces agitation.

This will drive co2 out of the water in most cases. Focus on flow and Lower your outlet to a gentle ripple. Healthy plants produce good amounts of o2.

Please do not ignore co2.

It moves slowly in water and the plants have a hard time obtaining it even in injected tanks. If you are successful without supplementing co2 then congratulations you have found a balance with regards to the above factors that is not easy to achieve in most cases but this does not always work.

If your plants are struggling please rule out co2 deficiency before anything else as there is more than enough evidence out there to suggest that co2 is the major limiting factor when it comes to growing aquatic plants.

Hope this helps and thanks for taking the time to read.

Cal.
 
Awesome post mate I could not agree more with all your statements. The main factors of balance and strong growth in my aquarium was due to increased flow rate and high injection of co2. Once my flow was strong and my co2 hit between 30-40ppm of co2 my plant growth was amazing and all algae became non existent.

I believe drop checkers give people false hope as mine stays yellow most of the day with no effect to my fish but my plant growth is strong because of it. Once co2 and flow is optimal then plant growth is just amazing to watch and is noticeable daily.

The chemistry of fish tanks is very very interesting and I can tell u have done a lot of research to back to your findings.

A+
 
Cheers bud

It is alarming to me how so many of us take co2 for granted. Myself included at one time.

Just wanted to get this out there so that people can understand how important it is and hopefully if things are not going right they can cross some of the things mentioned above off their list. [emoji846]
 
Cheers bud

It is alarming to me how so many of us take co2 for granted. Myself included at one time.

Just wanted to get this out there so that people can understand how important it is and hopefully if things are not going right they can cross some of the things mentioned above off their list. [emoji846]


Where's that new tank of yours? ;)
 
Ooh nice! U going to get Lilly pipes and an inline heater to get the full nano look?
 
Ooh nice! U going to get Lilly pipes and an inline heater to get the full nano look?


I'm not sure yet mate. I'm stuck with this JBL e1501 canister now that would be pushing 20x turnover. I'm not sure if I want the hassle of a canister any more despite the awesomeness of using a spray bar. Will update in the new thread. Got someone coming tomorrow to look at the vision 180.
 
I'm not sure yet mate. I'm stuck with this JBL e1501 canister now that would be pushing 20x turnover. I'm not sure if I want the hassle of a canister any more despite the awesomeness of using a spray bar. Will update in the new thread. Got someone coming tomorrow to look at the vision 180.


Good stuff I'll save all my questions for the new thread haha. I'm a canister man myself. I've got 4 running all my tanks at the moment haha
 
I've been dosing my planted tanks with Seachem Excel for some months now and see a definite improvement. I suspect it is what enabled the duckweed proliferation in my feeder tank, since they started around the same time.
 
I've been dosing my planted tanks with Seachem Excel for some months now and see a definite improvement. I suspect it is what enabled the duckweed proliferation in my feeder tank, since they started around the same time.


Being a floating plant duckweed doesn't normally need any help with co2 but it could well have sped things up for sure.

What other plants do you have?
 
I have in the feeder tank: Anubias, Java Moss and a tall grass-like plant I don't remember the name. The Goldfish tank has Anubuas and Swords. The goldfish are tough on plants. That is still in a development stage, having been re-started only a couple of months ago, while the feeder tank has been thriving since sometime early this year.

I plan to modify my goldfish rotation scheme to better support a planted tank next year. I've been moving them in and out of a pond and re-starting their inside winter aquarium home for the past three years. Next year I will continue maintaining the goldfish tank over the summer with a few small new inhabitants in order to get it more thoroughly planted and properly established. I suspect it may end up actually being less work in the long run doing it that way.
 
I have in the feeder tank: Anubias, Java Moss and a tall grass-like plant I don't remember the name. The Goldfish tank has Anubuas and Swords. The goldfish are tough on plants. That is still in a development stage, having been re-started only a couple of months ago, while the feeder tank has been thriving since sometime early this year.



I plan to modify my goldfish rotation scheme to better support a planted tank next year. I've been moving them in and out of a pond and re-starting their inside winter aquarium home for the past three years. Next year I will continue maintaining the goldfish tank over the summer with a few small new inhabitants in order to get it more thoroughly planted and properly established. I suspect it may end up actually being less work in the long run doing it that way.


Sounds like a good plan. When you say you noticed improvements by adding excel. What exactly did you see?
 
Plants that seemed to previously be just surviving now appear to be growing and thriving. Duckweed appeared out of nowhere. I really have no idea where it came from. Must've hitchhiked in with something I got from one of the fish stores somehow. Here it is:

20gal01.jpg


The Anubia on the right is suffering because I left it out of the water after forgetting it on top of the big tank last week. I pull it out every couple of weeks or so to take the mess of snails all over it upstairs for the Puffers. Any idea what the big one on the left is?
 
Duckweed is a weed. Period. On my naughty list for sure. Just ONE leaf can lead to hundreds.
The lengthy plant on the left side of the tank appears to be Pogostemon stellatus 'octopus'. In the right conditions it can be a rapid grower.
 
Duckweed is a weed. Period. On my naughty list for sure.

My Cichlids and Goldfish love it. They would probably eat 10 times as much as we're getting out of the 20gal if I had it.
 
Duckweed seems to have become an excellent part of the food chain in my little ecosystem(s). The little 20gal feeder tank is the most heavily planted including the weed, with the heaviest bio-load as well, by it's very nature. I need to stay on top of it, removing shrimp, guppies, snails and duckweed on a regular basis. It always returns the highest nitrate test level. Everything I pull out of it disappears into the bellies of the fish in the bigger tanks within a day. Usually withing minutes in the case of the guppies and shrimp. Duckweed has never been visible in the cichlid tank for more than a few days before it's all gone.
 
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