C02

[LetsBeFriends]

what is the purpose of having a c02 supplier in a tank?

 

[chr15_8]

what is the purpose of having a c02 supplier in a tank?

people inject co2 into there tanks to help with plant growth. unless you meant o2?

 

[Bignose]

carbon dioxide, CO2 (please note the use of capital C and capital O ("oh") -- the letters are the chemical symbols, C for carbon and O for oxygen), is primarily used to stimulate plant growth. Often, the levels of CO2 in a tank are too low for really good lush plant growth.

CO2, because it can form an acid, carbonic acid, can also be used to pH control. A certain rate of carbon dioxide injection can correspond to a certain pH.

However, both of these uses are for very advanced fishkeepers, and the vast majority of fishkeepers do not need to use them. If you poke around the planted tank forums, you can find lots of people talking about CO2 injectors to help their plant growth.

 

[LetsBeFriends]

thanks for clearing that up, i did not know if it was something i would need to be concern with, obviously it isnt

 

[Spooky76]

I would say unless your very experienced with fish, dont mess with it. I dont do it cos I wouldnt have a clue, but also I believe that the more CO2 you add the more O2 you drive out....so you need to know what your doing really.

If its for your plants, you can get some good plant food around now which helps.

But as Bignose said...leave it for the experts

 

[Bignose]

but also I believe that the more CO2 you add the more O2 you drive out..

But, see, this isn't completely correct either. The solution of the gases by the water are almost completely independent. The amount of other stuff in the water is very, very small.

However, what does happen is that because if you inject CO2, there are high levels of CO2 in the water, and when the CO2 gets to the surface, it wants to leave the water and enter the atmosphere. The more ripples and bubbles and general disturbances on the surface, the easier it is for gas-exchange between the water and air to occur -- hence the more disturbances, the more CO2 leaves. But, also, the more disturbances, the more O2 enters the water. Usually, the filter return is more than sufficient to allow O2 to enter in

So, there has to be a balance struck. Lots of disturbances means lots of O2 coming in, but most of the CO2 you inject leaving. No disturbances mean you keep a lot of the CO2, but the O2 entering may become limited. It gets even more complicated because when the lights are out, the plants don't taking in CO2 anymore, they actually take in O2. So, different balances have to be stuck during the day and during the night.

The levels of O2 and CO2 are related via the surface gas exchange, but it isn't just because of the more CO2 you put in that pushes more O2 out. It is a small but important distinction.

 

[LetsBeFriends]

wow, that sounds like a really really involved process, do people actually have different currents for different times of the day to allow different exchanges??

 

[Ian H]

no, most people just turn off the CO2 at night (be it via manually turning it off or automatic) or turn on an air pump

plus dont forget if your adding CO2 it means you have a decent amount of plants, which will take in the CO2 and give out O2. You may have heard of pearling? if not its when plants are growing amazingly and giving off so much O2 bubbles of O2 form on the leaves

 

[LetsBeFriends]

that sounds pretty cool, i do not have plants but i am looking to do it when i upgrade to a larger tank

 

[SuperColey1]

carbon dioxide, CO2 (please note the use of capital C and capital O ("oh") -- the letters are the chemical symbols, C for carbon and O for oxygen), is primarily used to stimulate plant growth. Often, the levels of CO2 in a tank are too low for really good lush plant growth.

Maybe just phrased wrong but CO2 isn't used to 'stimulate' plant growth. Carbon is an essential nutrient source for plants, just as NPK and trace elements (fertilisers) are, as it is what their main component is. Therefore no carbon - dead plants. There is a smal amount of CO2 as ther is O2 that enters naturally via the gaseous exchange so a low light tank can grow slow low light loving plants using the small amount of natural exchange.

CO2 is used mainly on medium to high light tanks as the plants will grow faster under high light and need more carbon than the natural exchange provides. In nature the water is continually moving along or in the case of stagnant ponds has a far greater surface area. therefore carbon is transported continuously. In our tanks the CO2 isn't continuously replenished it depletes and with high light and fast plant growth once it reaches zero then the plants stop!

So, there has to be a balance struck. Lots of disturbances means lots of O2 coming in, but most of the CO2 you inject leaving. No disturbances mean you keep a lot of the CO2, but the O2 entering may become limited. It gets even more complicated because when the lights are out, the plants don't taking in CO2 anymore, they actually take in O2. So, different balances have to be stuck during the day and during the night.

Most planted tank people don't strike a balance in this way. They decide if they want water turbulence or not and adjust the CO2 injection up or down to compensate for gaseous exchange. Also different balances don't have to be struck at day or night. In nature the CO2 doesn't disappear when the sun goes down. In a similar way there are many of us that run CO2 24/7. We do reduce the amount we inject but the water wil still have roughly 30ppm CO2 in it!!

Another reason for doing this is why turn CO2 on and off. CO2 reduces Ph by approx 1Ph. If you turn it off at night then your Ph is going up and down all the time which is not very good for the fish!!!

Andy

 

[Bignose]

Well, stimulate was the wrong word, but I didn't want to get into the whole thing with a relatively new member.

But, there are many people who turn off their CO2 at night, or at the very least turn it down, and turn on an airstone. I'm sure in some setups it isn't necessary, but in some I think it is. People do it because they found if they didn't, they would wake up to fish gasping near the surface.

Also, the pH swing isn't as terrible as you make it out to be. In nature, pH swings are part of daily life. Lakes and ponds with significant vegetation can experience pH swings over 1 pH unit in a span of an hour or so. It's actually the same thing you talk about here, because that occurs when the sun comes out and the plants start their processes. Also, even more dramatically, the wash off from a hard and fast rain is rarely the same pH of the body of water, but there aren't massive fish kills every time a hard rain occurs. Healthy fish can adapt to changes, even quick ones, pretty well.

Besides, even if you do leave the CO2 on at the same rate at night, the pH still changes some because the plants aren't taking it up anymore. The equilibrium shifts at night no matter what you do.

Finally, I don't understand how your description of "striking the balance" is different than mine. I talk about disturbances, and you talk about turbulence, but that's exactly the same thing (at least in my mind). And, at night, whether the fishkeeper turns the CO2 off or not, again, the equilibrium (or balance) has shifted. I guess it doesn't matter if the fishkeeper choose where is shifted to or not, but it does shift.