Please explain CO2

[Quatro]

Hey,

I can't grasp the purpose for an elaborate CO2 setup.  I know that plants use CO2 and produce O2 so it is definately a good ideal.  The problem I have is the CO2 setups release one bubble about every 3 seconds and standard airstones release thousands of bubbles per second.  Air is 80% cardon-dioxide.  So wouldn't that be a cheaper / easier way???  I figure I'm wrong but it makes sense to me.

Mike S

[BigDaddy]

Air isn't 80% CO2.  That's nitrogen.  CO2 is about 0.04 percent.

The amount of CO2 naturally present in a tank is 9 ppm.  That's basically from CO2 in the air coming into balance with CO2 in the water.

You can run an airstone all day, but you'll never get a higher concentration of CO2 in the tank, simply because there isn't a higher concentration of CO2 in the atmosphere.

I'll be covering CO2 in detail this Monday at the OVAS meeting.  You might want to attend.

[darkdep]

I had actually read that the concentration of CO2 in a tank from the atmosphere would only reach 2-4ppm; didn't think it got as high as 9ppm.

Plants need CO2 as a carbon source to build themselves.  There is some present as BD said, plus your fish will produce some.  But, any excess in the water above and beyond the atmospheric balance will just leak out at the water's surface given enough time.

The theory is, If you can raise the amount of CO2 in the water, then the plants have more building material available to them.  This, in combination with the other elements needed for good growth (light, macro and micro nutrients [fertilizers]), will allow them to grow faster.

If you want to raise the level of CO2 in the water, you need a CO2 source (for the purpose of this discussion, it's not important whether it's a scuba tank or a DIY generator), and you need to pump it into the water using a method that allows it to dissolve into the water faster than it escapes.  You also want to minimize surface agitation to slow down the CO2 escape and keep it in the water long enough for the plants to use.

I have a DIY generator on a planted tank, and have raised the CO2 to a level of 20ppm.  I am a believer in CO2 now, after seeing the difference it makes.  My hornwort grows over an inch A DAY.

[motoman]

How are you injecting your CO2 darkdeep?

[darkdep]

In my planted tank I use one of these:

http://www.bigalsonline.ca/catalog/product.xml?product_id=19239;category_id=2873;pcid1=3349;pcid2=

Some will say it's not the "most" efficient way to dissolve the bubbles, but it is effective in my 30gal tank and quite honestly, I like the way it looks.  

So, I have the 2L pop bottle with the yeast/sugar/water mix, I drilled a hole in the cap for the tubing (silicone tubing), and I run it to this thing with a check valve somewhere in the tubing (Cheap little thing to make sure water can't siphon back into the bottle).

That's it.  I empty the bottle and mix up a new batch when I see the bubbles slow down, which so far is about once every 2 weeks or so.

[NjOyRiD]

how do you know if the co2 is effective in the tank?

[Seanc]

usualy you will want it if you have more than 2 watts per gal for your lighting, but i'v found that it also makes the plants grow better in a low light tank, just not that much. When you have more then 2 watt per gal it is almost necisiary(sp) to have co2 because it helps keep algea under controle (i'm not sure how this works though) Hope this hellps

[BigDaddy]

usualy you will want it if you have more than 2 watts per gal for your lighting, but i'v found that it also makes the plants grow better in a low light tank, just not that much. When you have more then 2 watt per gal it is almost necisiary(sp) to have co2 because it helps keep algea under controle (i'm not sure how this works though) Hope this hellps

You do not NEED to have CO2 at over 2 wpgs.  Usually, at about 3 WPG CO2 becomes a necessity, and even then if you have a tall tank sometimes not.

[frollo]

I use one of those bubble counters too darkdep and I find it pretty efficient compared to using an airstone. Also it is much easier to know when the yeast solution is dying down

[darkdep]

NJoyrid:  I measure the CO2 concentration; right now the combo I'm doing keeps the measurement at 20ppm, which seems to be working well.  I haven't had a super amount of success with plants in my other tanks; in my planted "experiment" tank I'm running about 2.6 WPG and the CO2, plus proper ferts.  Dunno if it's any one single element, but the combo is working well.

A lot of others put the CO2 tube into a filter intake so the bubbles get all chopped up by the motor...this is probably a lot more efficient, but right now I have no complaints with the bubble thing.  The snails and shrimp like to climb on it, too.  

[NjOyRiD]

20 ppm,  how many degrees is this??

[BigDaddy]

20 ppm,  how many degrees is this??

There are no degrees njoy.  CO2 is only measured in parts per million.

[NjOyRiD]

oh...and how can I mesure the co2 concentration?

[DARKPHREAK]

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

[darkdep]

That's exactly the resource I use.  You basically measure pH and kH and make a determination based on that.  It's an indirect method, but if you measure before putting in CO2 and then after you can see the ph change as a result of your injection.

[NjOyRiD]

ah yeah, i remember now LOLOL forgot about thsi chart, thanx guys!