# DIY C02 w moving bed filter ?



## Fishfur (Mar 4, 2012)

I've been thinking about how best to get the C02 from a DIY bottle dissolved into the tank water of a 30 G tank. Don't have a HOB or canister filter. I use a sponge and a small air driven inside canister. Thus an inline reactor won't work. 

I have been interested in the new moving bed filters that I've seen online lately, and am considering trying to make one. They use an airstone bubbling up through a bottle filled with a moving media that gets colonized with bacteria, and is a good denitrifier.

Obviously there would not be enough air movement with just the CO2 from a DIY bottle, but if I added another air line hole to the moving bed filter bottle and ran the CO2 into it at the bottom, the CO2 bubbles would get chopped up, I think, by the moving media as it churns, before it gets to the top and exits with the rest of the air and water. 

One thing I'm not sure of is whether running the C02 into the filter media would kill off the bacteria that is supposed to colonize it ? It's not going to be anywhere near pure C02, but would it be enough to suffocate the bacteria to the point they would no longer be effective for their original purpose ?

Is there some other way to effectively dissolve the C02, where there isn't enough pressure to use a diffuser and you don't have a canister or HOB filter ?


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## Darkblade48 (Jan 28, 2008)

If you are using a sponge filter, and are thinking of moving to a fluidized bed filter, I don't really see the point of injecting CO2. The huge increase in surface agitation using both of these methods will off gas the CO2 much too quickly, rendering the DIY yeast mixture ineffective.


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## Fishfur (Mar 4, 2012)

I was thinking of a moving bed filter, not fluidized bed filter. Or is it a case of both terms meaning the same thing ? Just so we both know what I meant, it's a bottle partly filled with plastic media bits with an air stone at the bottom. Holes at the bottom of the bottle let water in, holes at the top let water and air out, and the movement of the air and water upward through the bottle churns the media, which over time will set up a hardy colony of bacteria to denitrify. But I can see your point.. that it would churn so much the CO2 would be blown out too quickly to dissolve. So what is a good way to get DIY C02 to dissolve well ? I believe it will not work with a ceramic diffuser, due to lack of pressure. So do I have to use a HOB or canister filter to chop up the bubbles ? If I understand the inline reactor idea properly, DIY CO2 also does not produce enough pressure to work in an inline reactor ?


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## Darkblade48 (Jan 28, 2008)

Fishfur said:


> I was thinking of a moving bed filter, not fluidized bed filter. Or is it a case of both terms meaning the same thing ? Just so we both know what I meant, it's a bottle partly filled with plastic media bits with an air stone at the bottom. Holes at the bottom of the bottle let water in, holes at the top let water and air out, and the movement of the air and water upward through the bottle churns the media, which over time will set up a hardy colony of bacteria to *denitrify*.


You have mixed up your terms (in bold). The bacteria are nitrifying, not denitrifying. The former is an aerobic process, while the latter is anaerobic. Denitrification converts nitrates to nitrogen gas. I believe some salt water aquariums use a plenum for this purpose.

In any case, the concept you have described is a fluidized bed filter.



> Fluidized bed filters consist of a vertical contact column in which water is pumped upward. Sand placed in the contact column is thus suspended by the upward flush of water. The trick is to supply a sufficiently rapid water flow to suspend the sand, but not so rapid that the sand is blown out of the top of the filter all together. The sand supplies a surface on which the desired bacteria may grow





Fishfur said:


> So what is a good way to get DIY C02 to dissolve well ? I believe it will not work with a ceramic diffuser, due to lack of pressure. So do I have to use a HOB or canister filter to chop up the bubbles ? If I understand the inline reactor idea properly, DIY CO2 also does not produce enough pressure to work in an inline reactor ?


Some ceramic diffusers may work, but it is hit or miss. As you mentioned, an inline reactor cannot be used as DIY CO2 does not generate enough pressure.

As such, if you do not want to use a HOB or canister filter, the only other method is with items such as disposable chopsticks, cigarette filters, airstones, and the like (porous materials).


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## Fishfur (Mar 4, 2012)

Thank you Darkblade,for the information, I appreciate it. There is always something to learn in this hobby, and you are a great source for good information. Now you mention it, I have seen a number of ads for a 'denitrifying' filter, called Aquaripure, and that is exactly what they say happens to the nitrites and nitrates it processes, and it uses anaerobic bacteria inside the filter. The end product is mainly nitrogen gas. Glad I have this straight now. Meantime, I went and got a small used power filter today. Originally I intended to use it in my brood tank for larval shrimp, and I was going to wrap all the water intake sections with 100 micron filter material, which I hope will prevent new hatched larval & newly morphed shrimp from being sucked into it. But after they are hatched I'll try it with the C02 and see how it does.


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