I recently set up DIY CO2 on my 2.5 Gallon Tank and I am trying to figure out the best way to diffuse it. There's not a lot of space, so it can't be anything bulky. Currently I just have a standard airstone on the end of the air line, but this doesn't seem to break up the bubbles much. I'm thinking about buying a wood airstone, which I understand should give me smaller bubbles, unless I can find a better method for this size tank.
CO2 Diffusion in a Small Tank
- Thread starter Purrbox
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krap101
Aquarium Advice Addict
i think people say ceramic air stones make the best diffusers.
Toker95
Aquarium Advice Regular
Most of the DIY C02 articles I've come across recommend ceramic airstones, if you go the airstone route. The consensus appears to be around the diffusing effects, and ease of cleaning / lack of erosion to the airstone.
The caustic effect of the yeast/sugar formula tends to attack the cheap plastic and wood airstones. Not a problem with pressurized, but then if you have the money for the pressurized, then you can probably afford even a cheap diffuser.
I'll have the last of the parts to get mine going here in a week or so. I intend to start out with a ceramic airstone, but eventually, as i save my pennies, build a power head diffuser.
The caustic effect of the yeast/sugar formula tends to attack the cheap plastic and wood airstones. Not a problem with pressurized, but then if you have the money for the pressurized, then you can probably afford even a cheap diffuser.
I'll have the last of the parts to get mine going here in a week or so. I intend to start out with a ceramic airstone, but eventually, as i save my pennies, build a power head diffuser.
krap101
Aquarium Advice Addict
ehehe pressurized co2 on a 2.5 gallon 
greenmaji
Aquarium Advice Addict
what type of filtration are you using?
malkore
Aquarium Advice Addict
and what's in this tank? 2.5 gallons isn't really enough room for a betta. is it plants only?
Well I've updated my signature with the basics on my two tanks so that should answer the majority of the questions about the 2.5. As to filteration it is a Azoo Palm Filter. It's been turned down pretty low and doesn't splash.
Back to the diffuser. I wouldn't mind buying a diffuser for the tank as long as it's small enough to hide behind the driftwood and/or plants. Unfortunately most of the one I've seen are fairly large and wouldn't even fit in my tank, let alone be readily hidable. Size is the issue, not cost (within reason).
I believe that the current airstone is ceramic, and it really doesn't seem to be doing any better of a job than simply having nothing on the end of the airline. Wouldn't the smaller bubbles from a wood airstone be better, even if it did mean having to replace it periodically?
Another option I though of, is using the outter part of a shringe (the kind they give you for liquid medicines) to create a bell diffuser. This would be a good size but I'm not sure how well it would work since it is tall and narrow and only has about a half inch diameter opening at the bottom.
I'd go the powerhead route, except that I don't think that I could get the parts small enough to fit in the tank.
Back to the diffuser. I wouldn't mind buying a diffuser for the tank as long as it's small enough to hide behind the driftwood and/or plants. Unfortunately most of the one I've seen are fairly large and wouldn't even fit in my tank, let alone be readily hidable. Size is the issue, not cost (within reason).
I believe that the current airstone is ceramic, and it really doesn't seem to be doing any better of a job than simply having nothing on the end of the airline. Wouldn't the smaller bubbles from a wood airstone be better, even if it did mean having to replace it periodically?
Another option I though of, is using the outter part of a shringe (the kind they give you for liquid medicines) to create a bell diffuser. This would be a good size but I'm not sure how well it would work since it is tall and narrow and only has about a half inch diameter opening at the bottom.
I'd go the powerhead route, except that I don't think that I could get the parts small enough to fit in the tank.
I was doing some browsing and found this diffuser which looks like it would be a good size for my tank. According to another site it is 1" diameter and 2.5" tall. Anyone have any experience with it?
What is your CO2 ppm and what size bottle/mix? I would think diffusion method isn't so important at such small volume.
HTH
Injection into the intake with small bubbles may allow the filter to stay quiet, functional, and give good diffusion while hiding equipment. Worth a try.
A small sintered glass diffusor is an excellent option -- ADA makes some sweet ones, but $$, as does Dupla. Flourish Excel can give you better control than DIY, which is unstable by nature, though less so when you run run more than one bottle and alternate mix changes. Just more suggestions.
You're right. You don't need an airstone at all though, and could just jam a cigarette filter of bamboo/chop stick into the airline: same concept and usually as or more effective (test).
HTH
Toker95
Aquarium Advice Regular
Purrbox said:
Is this one made of glass? or plastic? If I recall, this one was referenced on the site I prefer as a baseline guide for DIY CO2, can't find the link at the moment, but if I recall, it was highly recommended.
EDIT - found, via a post by GreenMagi... http://www.qsl.net/w2wdx/aquaria/diyco2.html
Other than airstones, I'd bet this would be the best option for such a small tank, especially since its only $15 in the first place.
Thats my .02 anyway...
I finally had a chance to test the parms on my tank.
dKH 2.2
PH 6.4
I did not find this combination on the chart, so I wasn't able to tell what the CO2 level is. Also if I remember right the chart can be off if you are adding anything to the tank that would affect either the PH or KH. I have a piece of driftwood in the tank and a couple piece of coral in the filter to buffer the KH (probably need to add another piece or two since it's still a bit low).
I am reluctant to inject the CO2 into the filter, as it doesn't take much to make it noisier (just resting at slightly the wrong angle is enough). I haven't found any specs on the size of the glass diffusers which is the main reason I've been avoiding them so far, that and I don't particularly like anything glass in my tanks in case of breakage.
I am currently running a single 1 liter bottle on the tank. In just a little over a week I plan to get the second one going. Then I'll change one every two weeks. I'm also adding a small amount of Flourish Excel (half does) to help keep things on an even keel.
While watching this tank the other day, I did see a little bit of pearling. I may just stick with the current setup for awhile and see how things go. I'll probably go with the Red Sea CO2 Reactor (which looks like plastic to me) if I still think it needs better diffusion.
dKH 2.2
PH 6.4
I did not find this combination on the chart, so I wasn't able to tell what the CO2 level is. Also if I remember right the chart can be off if you are adding anything to the tank that would affect either the PH or KH. I have a piece of driftwood in the tank and a couple piece of coral in the filter to buffer the KH (probably need to add another piece or two since it's still a bit low).
I am reluctant to inject the CO2 into the filter, as it doesn't take much to make it noisier (just resting at slightly the wrong angle is enough). I haven't found any specs on the size of the glass diffusers which is the main reason I've been avoiding them so far, that and I don't particularly like anything glass in my tanks in case of breakage.
I am currently running a single 1 liter bottle on the tank. In just a little over a week I plan to get the second one going. Then I'll change one every two weeks. I'm also adding a small amount of Flourish Excel (half does) to help keep things on an even keel.
While watching this tank the other day, I did see a little bit of pearling. I may just stick with the current setup for awhile and see how things go. I'll probably go with the Red Sea CO2 Reactor (which looks like plastic to me) if I still think it needs better diffusion.
greenmaji
Aquarium Advice Addict
It would be safer to have a slightly higher dKH value.. such as 3.. it really depends on how often and how much water you change..
A better CO2 reactor will likely make a world of diffence later on once you deside to do it..
A better CO2 reactor will likely make a world of diffence later on once you deside to do it..
I've added another descent sized piece of coral to the filter. I'll test the KH in a day or two and see if I've managed to get it up sufficiently and add more coral if necessary.
Also anyone have info on determining the CO2 levels in a tank other than that chart? For instance how do you compensate for the PH and KH being altered by driftwood and coral? If I could get some actual numbers on the CO2 in the tank, it would make it a lot easier to determine if I should go ahead and buy the CO2 diffuser or stick with an airstone.
Also anyone have info on determining the CO2 levels in a tank other than that chart? For instance how do you compensate for the PH and KH being altered by driftwood and coral? If I could get some actual numbers on the CO2 in the tank, it would make it a lot easier to determine if I should go ahead and buy the CO2 diffuser or stick with an airstone.
You can still get an idea of CO2 from the difference in pH from aged tank water. I think you'll have to go by observation of plants and fish to know appropriate CO2, and of course very small volume means very little room for error. FWIW, I'm guessing two 1L is way too much CO2, especially if you use an efficient reactor, and would try small soda bottles. (I use two 2L with an active diffuser to get >40ppm in ~15g with water agitation.)
I don't know if you can derive an exact CO2 ppm, but jsoong used to post a lot of info about buffers, and some posts in the archives may be applicable to your situation. Some of the threads he has participated in are linked in the CO2 sticky.
HTH
I don't know if you can derive an exact CO2 ppm, but jsoong used to post a lot of info about buffers, and some posts in the archives may be applicable to your situation. Some of the threads he has participated in are linked in the CO2 sticky.
HTH
I went back and reread the CO2 article based on czcz's advice and found lots of info that didn't sink in the first time around.
First off it looks like crushed coral and/or coral pieces will not throw off the CO2 readings, just using additives like PH Up etc. So I should be able to use the same measurements despite the driftwood and coral pieces.
I also found where the actual formula was posted for figuring out the CO2 levels: CO2 (in PPM) = 3 * dKH * 10( 7-pH ). This means my current CO2 level with only one bottle running and the inefficient airstone, is 26.27! Based on this it looks like I will have no need to switch diffusion methods, though I may need to downsize the bottles. Sigh, that means having to refigure the mixture for the smaller bottles.
Thanks for all your help everyone in helping me muddle through this and Kudos to you czcz!
First off it looks like crushed coral and/or coral pieces will not throw off the CO2 readings, just using additives like PH Up etc. So I should be able to use the same measurements despite the driftwood and coral pieces.
I also found where the actual formula was posted for figuring out the CO2 levels: CO2 (in PPM) = 3 * dKH * 10( 7-pH ). This means my current CO2 level with only one bottle running and the inefficient airstone, is 26.27! Based on this it looks like I will have no need to switch diffusion methods, though I may need to downsize the bottles. Sigh, that means having to refigure the mixture for the smaller bottles.
Thanks for all your help everyone in helping me muddle through this and Kudos to you czcz!
greenmaji
Aquarium Advice Addict
26.7ppm CO2 is high but not so high to be alarmed.. some people try to get 30ppm.. It sounds like your fine right were you are.. 
Yes, but I'm getting that much CO2 from ONE bottle, and I was planning to have two to keep the CO2 levels steadier. That's why I was thinking that I may have to downsize the bottles. The second bottle could easily push the CO2 levels beyond 35 ppm which is where fish could start to have problems from what I've been reading.
Now I have to decide whether I want to risk trying the second bottle as is and see where it puts the CO2 levels, or plan on down sizing and rotate the one liter bottle out at the next change. I think what I'm going to do, is retest next Tuesday (that's the day I have scheduled for the second bottle to start) to see what the level of CO2 is that point. If it's still pretty close to 25 ppm I'll start a 20 oz bottle, but if it's dropped quite a bit from that level I'll go ahead with the second 1 liter bottle.
Now I have to decide whether I want to risk trying the second bottle as is and see where it puts the CO2 levels, or plan on down sizing and rotate the one liter bottle out at the next change. I think what I'm going to do, is retest next Tuesday (that's the day I have scheduled for the second bottle to start) to see what the level of CO2 is that point. If it's still pretty close to 25 ppm I'll start a 20 oz bottle, but if it's dropped quite a bit from that level I'll go ahead with the second 1 liter bottle.
