Tropical Fish Keeping - Aquarium fish care and resources

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ghostgirl 01-07-2011 10:48 PM

CO2 confused
 
I am clueless about CO2 I know absolutely nothing other than plants need them. Can someone please walk me through it?

125 gl overflow tank
wide variety of plants

I know they can get expensive. I have a very trustworthy LFS but they are still trying to make a buck so I don't really trust them to give me the best low price options. Thanks in advance.

Byron 01-08-2011 12:01 PM

Jessi, aquatic plants need nutrients and light (just like terrestrial plants, although some nutrients are needed in different amounts or not at all). There are 17 nutrients required by aquatic plants, and in a fairly specific proportion. An excess or deficiency of certain nutrients will or may inhibit plant growth, depending upon the nutrients, the plants, the biological system, etc. Won't get into all that, but mention it because this matter of the amount of the nutrients will come into the discussion later.

Of the 17 nutrients, carbon is one, and it is essential to all plants. Terrestrial plants (so far as I know) all assimilate carbon from the air as the gas carbon dioxide (CO2). Carbon can be available in water in one of two ways, as CO2 and/or as carbonates. The latter is more prevalent in hard water, and can be non-existent in very soft water. Most plants can use either though they show (when given the option in experiments) clear preferences; mosses cannot use bicarbonates at all. As most of our aquarium plants occur naturally in very soft water, they have evolved to use CO2 as their preferred source of carbon.

CO2 occurs naturally in the aquarium in two major ways. Fish release CO2 via respiration, just as we do. Bacteria also release CO2, and in any balanced healthy aquarium, the bacteria actually produce more CO2 than the fish. There is more CO2 in a balanced aquarium than many realize, which is why we can grow plants so well without adding it, provided everything else balances too.

Plants assimilate CO2 from the water, and this is a slow process, about 4 times slower than terrestrial plants assimilating CO2 from air. Floating plants assimilate most of their CO2 from the air, which is one reason they normally grow much faster--they are close to the light, their roots and sometimes the leaves remove nutrients from the water, but their leaves being on the surface can assimilate much more CO2. The slow assimilation is why water movement and surface disturbance should be minimal in tanks with plants. The more the water moves, the faster the CO2 is moved past the plants before they can assimilate it. And more surface disturbance means more gas is being exchanged at the surface--CO2 is driven out, and oxygen is brought in to the water. Ironically, excess oxygen can be detrimental to plants too, because it binds with several micro-nutrients (such as iron, also essential to plant growth) and makes them unavailable to plants because the molecules are too large.

At the start I mentioned balanced nutrients. Plants need some in greater quantity--macro-nutrients we call them--and some in less quantity--micro-nutrients. Within these two categories are further proportional needs. The point behind this is that we have to ensure all nutrients are available, but that none are in excess. The CO2 comes naturally from the biological processes in the aquarium (which depends upon the fish load, water movement, and bacteria), as does oxygen, hydrogen and most of the nitrogen [as ammonium from the ammonia produced by fish and bacteria]. The other nutrients are usually added via fertilizer, although some occur naturally in fish food, from organics (waste broken down by bacteria in the substrate) and the replacement water at water changes.

I hope this has answered your question, but feel free to ask about anything that isn't clear.

Byron.

ghostgirl 01-11-2011 10:08 AM

upon rereading my op I wasn't quite clear about what I was asking. I want to know about the co2 systems and how to use them and the most effective and economical way of using it.

I apologize for making you go though all of that but hopefully it will help others as well. I do thank you for the information.

cmc29 01-11-2011 10:18 AM

i make my own CO2 in a 2 liter coke bottle, using sugar, water, baking soda, yeast. You should try researching DIY(do it yourself) CO2 systems online. That will give you something to think about. It sounds coplicated at first, but once you get started its very very easy. The only reason i add C02 to my tank is to help balance out the nutrients like Byron says. My light is pretty intense, so the C02 helps use all the light, making my plant growth very rapid, while keeping algae growth to a minimum.

Byron has a good point though...most setups will do just fine without C02. I prefer adding it to my tanks, it does make for explosive growth in my tank. I do a lot of trimminig

redchigh 01-11-2011 10:42 AM

I'd be cautious about using DIY CO2. If you don't get the recipe right, or don't replace the bottles on the right schedule you can get lots of algae...
If you really want to use CO2, then drop the money for a real setup. IT's TONS cheaper in the long run.
(True, Sugar and yeast are dirt cheap, but replacing a bottle every few days is more expensive than buying a 20Ib CO2 can and letting it last you 1-2 years.)

Regardless, I don't use CO2 because I don't think it's neccesary. Substrates, fish, and filter bacteria produce ample CO2 for my plants, and I'm content with the growth. I'd rather not do "lots of trimming", and spend that time watching the fish.

If you go with CO2, go with the more expensive compressed setup. CO2 is pretty easy to find once you buy the tank. (Try soda bottling companies :P ). Sometimes you can get a refill for 10-12 dollars. If you really want to drop some money, you can get a ph controller, so you don't have to worry about dosing the tank properly... Most of us here use tjhe "low tech" method, but CO2 users like to hide out. I would pm Redknee... I'm pretty sure mikaila uses CO2 too.

cmc29 01-11-2011 10:48 AM

Quote:

Originally Posted by redchigh (Post 556719)
I'd be cautious about using DIY CO2. If you don't get the recipe right, or don't replace the bottles on the right schedule you can get lots of algae...
If you really want to use CO2, then drop the money for a real setup. IT's TONS cheaper in the long run.
(True, Sugar and yeast are dirt cheap, but replacing a bottle every few days is more expensive than buying a 20Ib CO2 can and letting it last you 1-2 years.)

Regardless, I don't use CO2 because I don't think it's neccesary. Substrates, fish, and filter bacteria produce ample CO2 for my plants, and I'm content with the growth. I'd rather not do "lots of trimming", and spend that time watching the fish.

If you go with CO2, go with the more expensive compressed setup. CO2 is pretty easy to find once you buy the tank. (Try soda bottling companies :P ). Sometimes you can get a refill for 10-12 dollars. If you really want to drop some money, you can get a ph controller, so you don't have to worry about dosing the tank properly... Most of us here use tjhe "low tech" method, but CO2 users like to hide out. I would pm Redknee... I'm pretty sure mikaila uses CO2 too.

@redchigh I agree that anyone should be cautious using DIY CO2. However, with all due respect the bit about replacing it every few days is absolutely NOT CORRECT. I make a new recipe every 3- 4 weeks. 2 cups sugar, 1 teaspoon baking soda, i packet of dark yeast....all very very inexpensive, even over years.

It's not the canister that is expensive when buying a CO2 system...it's everything else that you have to buy to go with it.

redchigh 01-12-2011 10:14 AM

True, but that stuff pretty much works for the rest of your life. It's a one time purchase.

How much light to you use over your DIY CO2 tank?
Do you have steady 1-2 bubbles per minute for the entire two weeks?

Mr Fishy 01-12-2011 01:07 PM

The overflow is going to be an issue as well because it's going to allow the C02 to escape. Heavily planted tanks with C02 addition would ideally be completely calm on the surface.


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