CO2 Question

[AZdogpatch06]

I was watching a YouTube video about a filter review. There was a comment made in the video about CO2 that caught my attention and I thought I'd bring it to the boards. The guy mentioned that the filter greatly agitated the surface of the water, causing some CO2 to be lost. I was always under the impression, and taught, that we have to agitate the water surface to diffuse oxygen into the water. I used to use air stones to do this, but I now use a power head in both my freshwater and marine tanks. Now I'm sort of confused. I've never considered injecting CO2 into my freshwater tank. One time I was told you only need to do this on very large, 55+, gallon tanks that have hard-core lighting.

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[Mebbid]

Co2 is a bit of a balancing act. It's easy to bring it too high killing your fish but its also hard to get high enough. There's a goldylocks zone right in the middle to help plant growth without gassing your fish. You are injecting co2 to feed your plants but just enough to keep at a consistent level while it gasses off.

 

[BBradbury]

O2 and co2

AZ...

If you agitate the surface of the tank, you will drive off CO2. This is why you don't want strong filtration in a heavily planted tank. I've noticed this in my larger tanks. The heavier the filtration (more surface movement), the poorer my plants did. This is why I removed all the air stones from the tanks and got smaller filters, a gallon per hour (gph) rating 4 times the tank's volume is plenty. My plants started to improve in a few weeks.

Low light plants don't require added CO2. If you keep the tanks open, there's plenty in the surrounding air and in the dissolved fish wastes to support them. I keep varieties of Anubias, Java fern, a couple of kinds of moss, Anacharis, Hornwort and Pennywort. They grow fine with a couple of florescent bulbs from the hardware store.

Attached is a pic of low light 38 G tank with minimal filtration, not much surface movement, no ferts other than what the fish provide and lots of large water changes. The floating plants need to be thinned about every couple of weeks. Looks like I need to get busy.

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[AZdogpatch06]

Wow your tank does look slightly over grown! Anyways, in that case, how are we supposed to oxygenate the water for our fish? Also, I can't keep my freshwater tank open. I've got two African dwarf frogs that would likely jump out.

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[Mebbid]

Wow your tank does look slightly over grown! Anyways, in that case, how are we supposed to oxygenate the water for our fish? Also, I can't keep my freshwater tank open. I've got two African dwarf frogs that would likely jump out.

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The filter is generally more than enough to oxygenated the water by itself. If you see fish gasping at the surface then you will need to look into more options to increase oxygenation.

 

[AZdogpatch06]

I've got a powerhead in both the freshwater and saltwater tanks to help with water and oxygen movement. Just got some new plants today for the freshwater tank and I'm starting a liquid CO2 dosing regimen to go along with the grow light I have. Hopefully my plants will go nuts!

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[Mebbid]

I've got a powerhead in both the freshwater and saltwater tanks to help with water and oxygen movement. Just got some new plants today for the freshwater tank and I'm starting a liquid CO2 dosing regimen to go along with the grow light I have. Hopefully my plants will go nuts!

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What light do you have over the tank?

 

[AZdogpatch06]

It's not very powerful. It's just a flormax T8 light on the 20 gallon.

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[Mebbid]

It's not very powerful. It's just a flormax T8 light on the 20 gallon.

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Ahh, gotcha. Are you using excel? With that you should notice an increase in growth, but it won't be a crazy change. Light is a big factor in limiting growth of plants so with a low light level there's generally a slow growth rate.

 

[AZdogpatch06]

My CO2 liquid? It's made by api. It's called CO2 booster.

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[AZdogpatch06]

I've been considering a T5 set up on the freshwater tank.

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[ScotJudd]

Hi.
Mebbid summed it up - it's a balancing act. I run my tank with the filter outlets about 2" below the water level, inject Co2 when the lights are on and run air stones at night to assist driving off both the Co2 not required by the plants and the Co2 produced by the plants at night. I carefully control the Co2 injection to keep it at a comfortable level for the fish using a drop tester and a good quality bubble counter. I'm not sure if this control is so easy with DIY Co2 as I've not used it.


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