Dissolving DIY C02 in a HOB filter
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Old 07-24-2009, 12:44 PM   #1
njenner
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Dissolving DIY C02 in a HOB filter


Hi,

I'm just looking to get some opinions on my DIY C02 setup. I know there are several ways to get the C02 dissolving but here is my current method-

I'm running an airline from the DIY bottle and ending it with a small airstone which sits just under the HOB filter intake.

The very fine bubbles are being sucked up directly into the filter thus also being put through the impeller.

Is it likely that this setup would actually see the C02 dissolving into the water?

Thanks
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Old 07-24-2009, 02:38 PM   #2
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The CO2 is very likely dissolving into the water, but also very likely escaping from the water as it is returned to the tank. I think it is best to either introduce the CO2 in a closed system, like a canister filter system, or directly into the tank, like with a ceramic diffuser. Otherwise you lose too much of it "in transit".
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Old 07-24-2009, 02:38 PM   #3
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The impeller would probably not produce smaller bubbles than the airstone already does, but those bubbles would likely be in contact with the water longer because they're going through the filter. So that's a good thing... but I'd have to agree with Hoppy that a ceramic diffuser would be better.
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Old 07-24-2009, 04:54 PM   #4
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Quote:
Originally Posted by Hoppy View Post
The CO2 is very likely dissolving into the water, but also very likely escaping from the water as it is returned to the tank. I think it is best to either introduce the CO2 in a closed system, like a canister filter system, or directly into the tank, like with a ceramic diffuser. Otherwise you lose too much of it "in transit".
I agree to a point.
With a HOB some of the CO2 is lost due to turbulence in the water being returned.
However with DIY CO2, itís difficult to build up enough pressure to drive the CO2 through an airstone or ceramic diffuser.
When I tried it through a ceramic diffuser I thought the bottle with the yeast mixture was going to burst before bubbles came out of the diffuser.
So I ran the CO2 line directly into the intake of a HOB filter.
On a 10 gallon with mineralized substrate and no fish,
I checked the pH level before starting the CO2.
The pH was 7.0. Thirty hours later the pH had dropped to 6.8 and now is about 6.7 to 6.8.
So some CO2 does dissolve into the water.
By far the best method I use is pressurized and injected into the intake of an XP2 canister.
I have the pH controller set at 6.6 and I could easily drop the pH lower but I donít want to hurt the fish.
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Old 07-24-2009, 05:31 PM   #5
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I have bubbled CO2 into the inlet of an AquaClear Mini (20) for several years, and it worked great. Sure there is some loss due to the HOB surface agitation, but the impeller did a good job smashing up the bubbles, and for smaller tanks the CO2 loss is not a big deal.

I would lose the airstone if you don't mind the noise of the bubbles hitting the impeller. An airstone is bad news for a DIY CO2 setup, it creates backpressure and might eventually clog.
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Old 07-24-2009, 05:37 PM   #6
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I am using the exact same method, personally I think it works well enough to do what you need it to.

I think some of the other responses are forgetting a few things. If you are using a HOB filter, let alone DIY co2, as I am, I imagine you are trying to do this tank on a budget. Given that, pressurized co2 and a canister filter with an in tank diffuser are probably not realistic options. Additionally, I am not entirely convinced that this method is not nearly as effective as any other. I say that because with a fine enough airstone, you are starting with very small co2 bubbles to begin with. From there, these small bubbles are being pulled in to your HOB, and being vigorously mixed by the HOB impeller. And even beyond that, if you have fine filter pad in your HOB, the bubbles are being caught by this and held in place while water rushes past, providing even more contact time with the water.

I'm not arguing with the replies saying pressurized co2 with a canister filter and ceramic diffuser is more effective, I just think everyone has a different level of "good enough," and if you're on a budget, at some point you need to realize that stressing out and over thinking things is going to end up distracting you from simply enjoying your tank.
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Old 07-24-2009, 11:37 PM   #7
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I've bought a small glass Rhinox difusser from ebay and when it arrives i'll put that in and see how it goes. For now i'll keep the same setup as above.

Thanks a lot for all of your feedback, i really appreciate it.
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Old 08-06-2009, 12:34 AM   #8
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I may be a little late to join the conversation but here it goes..

I recently purchased a diffuser on ebay. it did take quite a bit of pressure to get the air to push through the ceramic. Then a couple days later the pressure would just separate the airline hose from the diffuser. I think there was not enough pressure to push through the ceramic but enough to build up and push the airline and glass diffuser apart.

Today I said screw it and put the airline directly into the intake of my HOB280. I assume I may lose some more co2 but i will put some sponges in the back of the hob to reduce agitation. Sound like a good idea?

Quote:
Originally Posted by njenner View Post
I've bought a small glass Rhinox difusser from ebay and when it arrives i'll put that in and see how it goes. For now i'll keep the same setup as above.

Thanks a lot for all of your feedback, i really appreciate it.
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Old 08-06-2009, 03:40 PM   #9
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Quote:
Originally Posted by dsubaru View Post
Today I said screw it and put the airline directly into the intake of my HOB280. I assume I may lose some more co2 but i will put some sponges in the back of the hob to reduce agitation. Sound like a good idea?
You should be fine.
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Old 08-06-2009, 11:20 PM   #10
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i think that a significant source of co2 loss in an hob is the impeller well area. look at all the turbulence and surface agitation going on. seems to me that would be the first place co2 is being blown off.
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