View Full Version : In a non-Co2 injected tank, does an Airstone gas off Co2, or pull it in?
Rocketman
08-07-2003, 1:45 PM
A few days ago, DJLen said:In a non-injected tank CO2 will be added to the tank through gas exchange by aerating the tank and good water movement. Keep in mind that the CO2 concentrations in a non-injected tank are quite low 'Gassing off' occurs in CO2 saturated water. Aerating it will actually draw gas into the tank from the atmosphere(minimal though it may be).
I wasn't sure about this, it just seemed like it removed a long-standng belief that every fish tank should have an Airstone. THe rest of what I planned putting here can be found in another thread: http://www.aquariacentral.com/forums/showthread.php?s=&threadid=14382
Mostly, the meat of it is that every beginner has an airstone. Does this mean that they shouldn't have one?
CHINABOY1021
08-07-2003, 1:47 PM
gas off co2. plus you are pumping air into the tank and thats mostly oxygen.
GulfCstAquarian
08-07-2003, 1:50 PM
To answer your question directly - it pulls it in.
But that depends on a few things. If you're not injecting CO2, the levels of CO2 in the water depend on how much it can absorb from the air. So the airstone helps. But fish also release CO2 into the water as they breathe. So with a full fish-load, your CO2 levels could actually be higher than atmospheric. In this case, an airstone would cause that excess CO2 to be released into the atmosphere.
It has been my recommendation to always have surface agitation in a non-CO2-injected tank. Since plants aren't growing at vigorous levels, they aren't producing as much oxygen as the fish might need. The tank will also be much more stable and consistent with an airstone, HOB filter or other form of surface agitation.
Rocketman
08-07-2003, 1:52 PM
So a tank that is slightly under-stocked with a Canister Filter setup, (to produce low surface agitation,) such as mine would make use of an airstone.
But one more question for you all. I added Flourish Excel, (the "liquid Co2.") Now what?
GulfCstAquarian
08-07-2003, 1:55 PM
Right, an airstone would help stablize dissolved gases in your setup.
Flourish Excel does not provide Carbon in a gaseous form. An airstone would only help supplement that carbon with additional CO2 absorbed from the air.
Rocketman
08-07-2003, 1:59 PM
Good, Good. I don't want my plants to grow that much, (I am sometimes away from home for a week at a time,) I just want them to stay alive. I honestly couldnt care if they don't grow one inch next year...All I have now are an Amazon Sword, Bacopa, and some Anacharis, (which I don't think will work out,) along with some, (8 stems) of Ludwigia. Do you think this setup would support one or two more Swords? There is a large empty spot in the tank now where the Hornwart used to be. I'm deciding what to put there.
GulfCstAquarian
08-07-2003, 2:02 PM
I think a sword would do well in the low-maintenence setup you're aiming for. Even better would be a nice Anubias coffeefolia. A little more expensive, but a lot more hardy and slow/steady growth.
Rocketman
08-07-2003, 2:07 PM
And the lighting is only .5 WPG.
But I use Aqua-Glo, which are supposedly get spectrum.
Rocket Guy, the simplest way to put it is if the atmosphere has more CO2 in it than your water table, an air stone will draw CO2.
If the water table has more it will gas it off.
I do agree with the Gulf guy that in your circumstance an air-stone would be beneficial.
I do not believe that "every tank should have an airstone". In an injected tank they defeat the purpose.
Len
If the crabby old fish keeper can chime in, it will be a cold day in Sao Paulo when I have any fish tank with an airstone.
Do you have a filter? What makes you think that you (or anybody) need(s) an airstone? That usage dates back to the daye of small plastic box filters (air-driven of course).
With current technology, there is no excuse other than personal aesthetics for use of an airstone.
But whether or not such a device removes or adds CO2 does depend on the kinetics of the particular tank, as has been said. If the tank is lower than air-equilibrium for CO2, it will bring some CO2 in. If the tank is greater than air-equilibrium for CO2, it will blow some CO2 off. Individual tank parameter - if you can't test at that level, you will never know.
Blowing off CO2 to control plant growth is not a very good idea - the algae however will love it. With sufficient carbon (i.e., CO2 for most plants), the plants will use nutrients. Lacking CO2, they will stop growing and use less nutrient. Excess nutrients with insufficient carbon results in? This is a test. ;)
Well said Robert!!!!!:)
Len
Rocketman
08-07-2003, 6:59 PM
I will have to measure my Co2 in the water somehow, and then do some research about what it could be in the air...that sounds like the only way to tell.
cpr4cpu
08-07-2003, 7:21 PM
if you have low light (.5 wpg) then why even worry about CO2 at all. The photsynthesis will be slow in the low light that the fish themselves should be able ot produce enough CO2 for the low light plants.
Swords might like some some root tabs or other source of soluble iron in the substrate (flourite, laterite, or commercial root tabs)
Air equilibrium for CO2 in water would be ~2 to 4-5ppm, depending on your altitude above sea level and the barometric pressure at the time of measurement.
That is without any contribution from all the bacteria, infusoria, fish, and non-photosynthesizing plant mass in the tank - almost all the biomass in the tank can contribute to CO2.
Minimum supplement levels are generally given as about 15ppm CO2. Pressurized gas folk with high light aim a bit higher, toward the high end of 20-35ppm.
Rocketman
08-07-2003, 11:48 PM
I am using Root Tabs....
I heard once that an imbalance in Nutrients...does something bad to the plants.... For example, a high amount of Co2 and trace elements, but with a low amount of light is not good. So, maybe I should use up the remaining root tabs and Flourish Excel, and then just leave the thing alone?
The "something bad" is usually algae. Balance is the whole thing. If you have lots of plants, plenty of light, added nutrients but insufficient carbon/CO2/Excel, you have an issue. If you have low light, low carbon/etc., but high nutrients, you have an issue. Everything has to be in the same order of magnitude, or problems can arise.
I have the most problem at moderate light (~2W/gal. NO fluorescent), where I have enough light for steady slow growth of hungry plants such as swords, but not quite enought nutrient in the subatrate and barely enough carbon in the water. If I slip, bingo! - hair algae.
GulfCstAquarian
08-08-2003, 10:54 AM
I think we're overcomplicating this beautifually simple, low-maintenence tank. You don't need a CO2 test kit at this time. If you want to get one, by all means go for it. If you stay in the hobby long enough, you'll eventually have a pressurized CO2 system with a pH controller and the works. But for now, the beauty of this setup is its simplicity.
I do not propose the use of an airstone to blow off CO2 to control plant growth. Carbon should always be in plentiful supply, whether with the Flourish Excel or through CO2 gas. But cpr4cpu is right, with these lighting levels, light is the controlling growth factor so why overcomplicate things? Continue dosing the Flourish Excel and enjoy your tank! If you like how the airstone looks, keep it! I like them, too.
Sorry, GCA, but I do not agree with "If you stay in the hobby long enough, you'll eventually have a pressurized CO2 system with a pH controller and the works." I've been in this hobby >40 years, and although I do have a pressurized CO2 system, it is stored. Not everyone elects to go high tech. That is pure personal choice, not a foreordained progression.
Rocketman
08-09-2003, 10:16 PM
Hmm...yeah, I think things have gotten a little too complicated...
So how abou this? When a begginer comes into the Pet Store wanting to buy a tank setup, should they be sold an air pump and airstone? Assume they don't care either way as far as looks are concerned. And assume they will never put plants in the tank.
Now, same situation. Except this time, they want to put two swords into the tank, and they have bought root tabs for those two swords. They don't want to upgrade lighting, (currently at .5 WPG,) or add fertilizer. All they are adding is the root tabs. Now, should they use an airstone?
I see no reason for the airstone if they have an appropriate filter.
Fertilizer supplement at 0.5 w/gal is whistling in the wind.
All IMHO, YMMV. :)
Ranger
08-10-2003, 5:16 PM
Put in the air stone!
It won’t hurt or help the plants with the lighting and filtering in your tank BUT it will be a back up that might just keep your fish alive if something happens to your filter while your gone. (Being gone is the reason you said you didn’t mind slow growing plants and low maintenance).
RTR and GSA have both given you an accurate assessment based on their perspective of what you might be trying to accomplish.
Rocketman
08-10-2003, 8:10 PM
Then one final question. Assume they have those two swords, root tabs, and .5 WPG lighting. But they have a canister filter. Because of that, there is little surface movement has it is. Now what? Go with the airstone?
I don't know how many more times it needs to be said before it's understood but let's try just one......more..... time.
Airstones serve no useful purpose in a tank with adequate filtration. They are basically worthless.
With .5 watts/gal., you are wasting your time with fertilization.
Up your lighting to 1.5 watts, and lose the airstone. Then we can talk fertilization.
Len
Rocketman
08-10-2003, 8:25 PM
C'mon man...don't be too harsh....
On an unrelated note...I know we all measure lighting by watts. But it if you have a new 15W Bulb, say, 16000K, a 15W bulb that's 5000K is better, right?
Originally posted by Rocketman
On an unrelated note...I know we all measure lighting by watts. But it if you have a new 15W Bulb, say, 16000K, a 15W bulb that's 5000K is better, right? Yes :)