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Excess CO2/algae problem?

Alysoun McLaughlin wrote:

>For the past few weeks, two subjects on this digest have caused me to
>tilt my head and wonder.  I suspect that they may be related...
>1)  CO2 is clearly a necessary additive for Amano-style, luxurious
>"Dutch" planted aquariums.  Such incredible results can't be achieved
>without it.  

Not necessarily.  It requires careful planning and the use of the right
plants, but you can have a _stunning_ tank. without supplemental CO2.  I
have won very competitive Home Shows with moderate light/non-CO2
supplemented tanks against  very beautiful CO2 supplemented high light

>However, you can achieve an impressive tank (the kind that
>even impresses other hobbyists) which requires two or three trimmings a
>week, has happily flowering plants, and nicely reddish tinges to the
>bunch plants, without adding even a DIY CO2 setup.  Ditto for the 3-4
>watts per gallon (I have 2).  It seems that often, beginners lurk on
>this list for a while, and are led to believe that, if they don't set up
>CO2 injection and a 'these-go-to-11' lighting setup, their ambulia will
>never survive. 


>Might I suggest an alternative solution to some of these algae
>problems?  Get rid of the CO2 and cut back to 2 watts per gallon? 
>Perhaps even cut back on the fertilizer?  You can always add them again
>later, but since you've clearly got algae exploiting resources that your
>plants aren't taking full advantage of...

It's not the CO2 that's the problem though - as you partially alluded to
with the mention of cutting back lighting too.  The important part is to
find an equilibrium for your system.  It's easier to do with a more
moderate amount of light.  At 2 w/g, many tanks will still benefit from
supplemental CO2, although they may do well without it also.  At 3 w/g most
tanks NEED supplemental CO2.  In the case of the 2w/g tank, adding CO2 will
not lead to algae problems.  At 3w/g, you probabaly _will_ have algae
problems if you _don't_ supplement with CO2.  

In EITHER case, you may have algae problems if phosphate/nitrate levels are
too high, (higher levels can be tolerated in the tank with lower light, but
you can't carry that to extremes) or if certain nutrients are in short
enough supply that it interferes with normal growth of higher plants.

Karen Randall
Aquatic Gardeners Association