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Re: CO2 or not CO2

On Sun, 13 Dec 1998, James Purchase wrote:


> I want to see if there are any qualatative differences between the major
> lines of aquarium fertilizers/substrates. If adding CO2 can be so
> problematic (insofar as ensuring equality among 4 separate tanks), perhaps I
> should just forego the use of supplemental CO2 altogether. That way, any
> differences in the tank would be more than likely due to the completeness of
> the fertilizers than it would be to more or less CO2 (and we all know how
> well CO2 can enhance growth).
> If I omit fish from the tanks during the period of the study I could cut out
> yet another variable.

I agree with removing the fish and using prepared nutrient solutions of
known concentration. If you really want to be precise, remove all of the
water each day and replace it with a fresh prepared solution. This means
that slow growing tanks do not accumulate concentrations of nutrients.
As a compromise, you might replace the water once or twice a week.
Without fish, it is easy to do a ~100% change; no need to condition the

I disagree with not using CO2 because you should make the nutrients in
the substrate the rate limiting factor. To dramatize the advantages of
the nutrients in the substrate making a BIG difference in growth, you
should ALSO fertilize each tank completely with all nutrients
(N,K,S,Mg,Ca,Fe,other trace) in solution. I think its going to be
important to maintain good circulation in each tank. I think you should
also add a small dose of phosphate, about 0.5 ppm each day. I think one
treatment should be reserved for a fertilized substrate, either with
clay balls or with Jobe's sticks (perhaps a soil one?). You could also
fertilize only one side of a tank, to observe how much difference there
is when the plant gets its nutrients at the roots, even though the
plants on the other side of the tank still get a boost from the
fertilized side by diffusion into the water column (and by sneaking
their roots over the line).

One method to deal with the CO2 factor, would be to give each tank a
measured dose of CO2 each day or several times a day. You could do this
by attaching an inverted glass to the side of the tank and filling it
with CO2 from a cylinder.

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!