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Re: Roger Miller, CO2 rates, 15 Jan

>snip ...I try to keep the plant population in the 55 gallon tank about
constant.  To do that I trim about enough every week to fill a small salad
bowl.  I think that's about 0.2 lbs (91 grams) per week, moist weight.  If
the plants are 6% carbon (85% water, carbon 40% of dry weight), then
they're fixing (and I'm removing) about 5.5 grams of carbon/week.  The
lights in that tank are on 12 hours/day, or 84 hours/week, so the carbon
fixation rate is about 65 milligrams/hour of light.  The corresponding CO2
fixation rate is 240 milligrams of CO2/hour snip...<

Perhaps I don't fully understand Roger's calculations; am I correct to
think they imply plants respire a lot of co2 without converting all that
carbon to plant mass? If so where does it go? I have tank conditions
(steady co2 injected, dKH 6) resulting in a pH change of .4 for each light
cycle but have very slow growth to show for it. Could this be symptomatic
of a particular nutrient deficiency?

Jeff Kropp