Filters and CO2 don't mix...?
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Old 12-28-2003, 03:32 PM   #1
Rolo
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For my ten gallon I was planning on hooking up my CO2 line to my AC mini's intake. The filter chops the bubbles and dissolves them for me...saving money and time from doing a DIY or buying a reactor. I read on a few websites though not to do this because the CO2 will starve the aerobic bacteria in the filter of oxygen, decreasing efficiency and turning them anaerobic where there already is plenty.

Can anyone validate/disprove this? In theory it mabey correct, but if experience says it doesn't cause problems, I don't see why not.
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Old 12-28-2003, 03:58 PM   #2
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I did the same thing but with a little differences.I drilled a hole below the motor so the co2 will be chopped into smaller pieces like you say,it is very effective...so far still nothing wrong with my filter.
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Old 12-28-2003, 06:20 PM   #3
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A bubble of CO2 here and there doesn't starve aerobic bacteria of oxygen. CO2 and O2 are not mutually exclusive. Adding CO2 doesn't reduce the O2 content of the water. It does lower the pH, and there are discussions about how that affects bacteria, and some think it's good for them and others say it's bad. I think the difference between adding the CO2 before or after the filter is negligible, considering the water flow that's going through the filter.

One word of wisdom though... the amount of CO2 that you get into the tank by bubbling it into the AC Mini inlet is minute. You observed right that the bubbles are chopped up by the impeller, but if you look closely you will see that most of them just bubble to the surface at the inlet side of the filter.

One thing you can do is to decrease the flow by moving the inlet towards the - sign. CO2 will then collect in the elbow of the overflow, and is more efficiently dissolved by the passing water. However, if you move it too much to the reduced position, and your CO2 production is too high, it might airlock after a while.
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Old 12-28-2003, 06:33 PM   #4
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What's the practical difference of running the CO2 into the filter and running it though a diffuser? If you end up with the same amount of CO2 in the water column it should cause equal harm to the bacteria. I run a external reactor and keep my large high light tank at about 30 ppm of CO2. And I still have bacteria in my filter. People that spread that kind of nonsense are either ignorant or malicious.

Here is an example that will really show the fallacy of this though. Take a room. Put two people in the room. One smoker and one person who is allergic to smoke. There is a fan in the room. The fan points toward the smoker. Seal the room and let the smoker light up. Does it make any difference whether the smoker blows the smoke into the fan or away from the fan?
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Old 12-28-2003, 11:28 PM   #5
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Ok, long but stick with it...good info to know

Quote:
Originally Posted by Wasserpest
A bubble of CO2 here and there doesn't starve aerobic bacteria of oxygen. CO2 and O2 are not mutually exclusive. Adding CO2 doesn't reduce the O2 content of the water...
I couldn't help but correct you wasserpest ...It's like a thorn in my flesh (I'm a chemistry student). It isn't a matter of CO2 decreasing O2, because your right they are "mutual", but the CO2 "blocks" the O2 from getting to the bacteria.

Here's some hard evidence: The Lake Nyos tragedy. I'll make a long story short: In August of 1986, a cloud of gas suddenly boiled from Lake Nyos in Cameroon killing nearly 2000 people. The lake is thermally stratified; layers of warm water at the surface sit on top of colder, denser water on the bottom. Normally the lake remains this way. For reasons unknown, CO2 has been supersaturating the colder water at the bottom for thousands of years. On that day monsoon conditions cooled the top layer and caused the lake to "overturn" its layers and releasing the huge amount of CO2 into the atmosphere. Basically what happened is that the CO2 "out-diluted" the O2 and the O2 was blocked from being diffused in their lungs. This is not only true of CO2 but of all dissolved stuff.

Quote:
Originally Posted by Rex Grigg
What's the practical difference of running the CO2 into the filter and running it though a diffuser? If you end up with the same amount of CO2 in the water column it should cause equal harm to the bacteria...
Yes, I thought this way first, but it isn't that simple. When you diffuse the CO2 in a tank or in the filter, there are two big differences; the tank has a lot more volume than a filter. Concentration is measure by the inverse relationship of two variables, amount/volume. When a bubble of CO2 is diffused into the whole tank, it has a lot of volume to cover but in the filter, the same bubble only spreads to a relatively small volume, upping the concentration considerably. This high concentration is only temporary for each bubble, since the CO2 rich water spills back into the tank diffuses further, but this water still has to go through all the bacteria and has the same effect as described by the Lake Nyos incident. Sorry if it was confusing, but being blunt, I know I'm right.

Conclusion
Ok, despite all this I see no problems with this method of CO2 diffusion. Ace, Wasserpest, and Rex I believe reflect experience of most here and myself that CO2 doesn't pose any problems to the bacteria in the filter. Everything I just explained is correct theory based on the most fundamental chemistry laws, but for practical purposes it obviously doesn't pose any problems; the amount of CO2 used in aquariums just isn't enough to suffocate the bacteria.

BTW, here's the link where I read not to put CO2 in your filter (click CO2).
http://paul.aaquaria.com/conditions/Pageset.htm
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Old 12-29-2003, 05:01 AM   #6
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wow...that's a long msg.. :shock:
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Old 01-19-2004, 05:57 PM   #7
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When doing DIY CO2, alcohol vapor is also coming out your CO2 line. For those of use who use thier filters as a reactor, does the alcohol negitively affect the bacteria? Are there any alcohol gas/CO2 gas seperators out there?
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Old 01-19-2004, 06:51 PM   #8
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Quote:
Originally Posted by Rolo737
does the alcohol negitively affect the bacteria?
The bacteria catch a buzz.............yahooo....party time. :lol:
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Old 01-20-2004, 03:40 PM   #9
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You can make a simple gas separator with a 20oz. soda bottle.
http://www.qsl.net/w2wdx/aquaria/diyco2.html#3
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Old 01-20-2004, 06:01 PM   #10
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Quote:
Originally Posted by malkore
You can make a simple gas separator with a 20oz. soda bottle.
http://www.qsl.net/w2wdx/aquaria/diyco2.html#3
I already have this "gas seperator" hooked up to my DIY which I use BTW as a bubble counter instead. simply, it doesn't! It shouldn't be called a gas seperator but rather a liquid/gas seperator. All this is made for is to let the yeast water (liquid) collect at the bottom.

Ok, I have to deal with this now, b/c its really starting to bug me. The most common misconception for why this simple 20oz bottle acts as a "gas seperator" is that different gasses sink and settle in layers. People think that since alcohol vapor is heavier than CO2, its will sink and let only CO2 escape. This is not true! Erase it from our memory and never think of it again! If this was true all the CO2 in the atmosphere would be at ground level and all of us would be suffocating.

Gasses have an relatively extremely high kenitic energy (motion) compared to solids and liquids; In a vacuum a gas molecule travels at thousands mph and in the regular atmosphere they are colliding like crazy with each other and constantly mixing. The fact that gasses have such relatively enourmous kinetic energy makes gravity (meaning also their weight since weight is a function fo gravity) irrelevant.

I think most people get hooked on this misconception because they have seen dry ice, which is frozen cold CO2, sublime into a gas and sink/creep along the floor. This is only becuase it is cold=alot more denser. And anyway, it quickly disappears in seconds because it reaches the room temp and mixs/spreads with the air. Gasses only settle b/c of different temperatures, besides that gasses never settle @ then same temp.

Sorry if I made the wrong assumption of how you were thinking Malkore, but I noticed alot of people think this way anyway so just had to deal with it.
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Old 01-20-2004, 07:04 PM   #11
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Anyway just to let everyone know, the original topic of this post was weather or not to use your filter as a CO2 reactor since it might harm the bacteria which is comprised of post 1-5. The conlusion is that it doesn't really harm the bacteria (Its a dense topic so read it for more clarification).

The topic now is if the alcohol vapor coming out with the CO2 is harmful to bacteria and if so, how to seperate it.
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Old 01-21-2004, 03:31 PM   #12
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Well here's my question, which I feel is related: in my blue ram tank, I run DYI CO2. I'm constantly fighting that white, snot-like, cottony buildup on the hagen ladder, and now the eheim diffuser. I was hoping a proper gas separator would fix the problem, but it hasn't. I don't think it's alcohol vapors but something in the yeast that's 'feeding' this mucus stuff...which by all accounts is totally harmless to the fish.
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Old 01-21-2004, 05:40 PM   #13
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I get the same stuff on one of my ladders. I just clean it once a week. I don' think it does any harm either.
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Old 01-21-2004, 07:47 PM   #14
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well thing is, it never appeared in my 29gallon tank, using the same DYI yeast setup. I'm gonna try something tonight, and I'll report back on it if it helps at all.
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Old 01-21-2004, 08:58 PM   #15
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Quote:
Originally Posted by Wasserpest
CO2 and O2 are not mutually exclusive. Adding CO2 doesn't reduce the O2 content of the water. It does lower the pH
Of course using an Airstone or a HOB filter disrupts the water surface so CO2 is released...

but what if one diffused O2 AND CO2 into a reactor ??

Would that keep you PH low AND enough O2 to not worry about your fish ever suffocating ??
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