I think most folks will tell you "it's all about balance." You need to
balance nutrients with each other and with energy input and with the types
of plants and fish load you plan to keep. That's why there's no pat answer
and also why balance takes time to achieve: unlike mechanical systems that
respond right away to input, living systems take time to respond and can
also complicate matters by storing nutrients for a time. This makes
determining the proper balance a time consuming matter that needs patience
and note taking.

To more directly answer your question: lower light means lower everything
else including carbon, nitrogen, phosporus, potassium and trace element
concentrations. OTOH, there's no problem I'm aware of with providing excess
CO2 in the 20-30ppm range.

jtm

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"Frank Mamone" wrote in message
. ..
I understand that optimal levels of CO2 should be 20-30ppm. I'm wondering if
in a low light tank like mine at 1.6WPG if less CO2 is optimal as less would
be used by the plants?

Thanks,

Frank