Co2 use in AquaPonics?

[Chi Ma]

Some of us that are transitioning into AP from the planted aquarium side have access to Co2. I wonder what the effect on plants will be like when Co2 is used. When injected into an aquarium, Co2 boosts a plants intake of nutrients and therefore growth. I have a small green house so as soon as I have everything in place I will try injecting Co2 atmospherically. I thought about doing it into the water but decided against it since Co2 uptake is usually done through foliage.

[TCLynx]

In flood and drain Aquaponics I doubt CO2 in the water would be appropriate anyway so injection into the air might have an effect, question will be, is it worth the cost.

[Chi Ma]

The cost for a refill of a 20lb tank is about $20 in my area. A 20lb tank services 120 gallons of water in my fish tanks for about 2 years. I'm figuring I will use double that releasing it into the air. So $20 a year doesn't seem too bad to me for a small scale operation like mine. I don't think it would be feasible for a large scale operation unless you get a Co2 generator and are in an enclosed greenhouse.

TCLynx said:

In flood and drain Aquaponics I doubt CO2 in the water would be appropriate anyway so injection into the air might have an effect, question will be, is it worth the cost.

[Sylvia Bernstein]

I actually heard somewhere that running aquaponics in a greenhouse relieved you of needing to inject CO2 because the fish give off CO2 into the air.  Anyone have thoughts on the validity of this?

[TCLynx]

Sounds logical

Sylvia Bernstein said:

I actually heard somewhere that running aquaponics in a greenhouse relieved you of needing to inject CO2 because the fish give off CO2 into the air.  Anyone have thoughts on the validity of this?

[Paul Letby]

Makes sense Sylvia.  I know it doesn't stick around in the water long when properly aerating.  I was injecting CO2 into my little fishtank water to boost plant growth, but decided to turn it off once I had such an overload in stocking.  I thought with all those fish I'll for sure have enough CO2.  Plants have slowed and algae is growing faster, but I'm also aerating the water now, so most likely CO2 being all offgassed into the air.  To go back though I hesitate, as the fish showed signs of stress before.

[Chi Ma]

I don't notice my fish being being stressed. They are actually happier. In my tanks when I inject Co2 the plants actually start pearling. the pearling is from increased o2 production. I only inject Co2 when there is light available for photosynthesis.

[Ryan Chatterson]

Gotta remember there is a difference between underwater plants and regular plants. Co2 levels in the air are pretty low, something like 300ppm. Plants will benefit from increased co2 levels up to something like 1200ppm. Growth rates have been shown to increase by something like 60% in certain species with 1200ppm co2 levels.

Injecting co2 underwater will also lower the ph, which you usually don't want to do in
AQ.

As Silvia said, putting your fish tanks in an enclosed greenhouse is beneficial because the offgassing of co2 from fish respiration raises atmospheric levels. If you do some googling, you will find some nice graphs plotting growth rates vs Co2 levels. It's a pretty linear increase until you get up to 1200ppm (ppm levels from memory, it's been a few years)

Chi Ma said:

I don't notice my fish being being stressed. They are actually happier. In my tanks when I inject Co2 the plants actually start pearling. the pearling is from increased o2 production. I only inject Co2 when there is light available for photosynthesis.

[Chi Ma]

Well I guess you don't get to be a pioneer by listening to the naysayers 

[Paul Letby]

You go Chi!