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Re: DIY co2 having no effect

On Mon, 29 Mar 1999, Carla Thorn wrote:

> Could anyone tell me why co2 injection in a 55-gallon tank would have
> practically no effect on the ph or plant growth? I have 3 bottles going at
> once--two 3.8 liter bottles and 1 half that size. All filled with the usual
> combinations of water, sugar and yeast and bubbling like mad into bell-type
> diffusers. (I've also tried airstones and feeding tubes into the intake of my
> two-biowheel wet/dry system.) The only surface turbulence comes from the two
> biowheels, but it's hardly a ripple. All tests look good (nitrate, ammonia,
> and nitrite not detectable; only phosphate is high, but I just added a pillow
> to bring that down). When I first tried injecting co2, my 7.5-80 ph came down
> to 7, but bounced back up to 7.5 and has been there ever since. What gives?

There's a few details you left out of your letter that you might want to

1) If your alkalinity is high, significant (to the plants) amounts of CO2
will have rather little effect on pH.  Check your alkalinity (KH).

2) You don't mention your lighting.  Adding CO2 won't have much effect on
plant growth unless without additions it is limiting plant growth. Often
it does limit growth and that's why we add it, but there are cases where
it might not be limiting; low light may be limiting growth.

3) Also, you don't mention how you're fertilizing.  As with low light, too
low nutrient concentrations can prevent CO2 from having the effect you

A couple other points...  I've tried using bells before, and I don't find
them very effective; different methods may get you better results.  Also,
your 3 yeast reactors are probably overkill.  I use a singe 1-gallon
reactor on my 55; the CO2 levels are low compared to what some people aim
for, but CO2 doesn't seem to limit growth.

Roger Miller