dwell for starters. a dc is only slightly accurate
i've been over the yellow range for a while. and yet i still increase my c02 if i desire
i am running high light ad i can turn them off all day and fish don't die
plants use very little of what we inject, more of its keeping concentrations high because there are low spots in the tank and higher concentrations fill the weak spots with mroe c02..
that's not exaclty how i wanted it explain
if ur injecting a tank average of 45 ppm. there will be spots that have 3-5 ppm due to flow and plant use. the plants don't actually need 45 ppm. they need the low spots to be higher... this is why we inject soo much.. its also why flow is SOOOO important
i only have a DC to make sure im still injecting c02. not to measure the quantity. FISH and plants are my measurments.. watch how your fish respirate daily for weeks and weeks, adjust c02 while u do so. you will learn what is acceptable and what is not quickly by this method.. the plants will always accept more. fish won't.
one way also to tell if there is too much, is watch their habits with c02. as it ges higher its a lot like a sedative, they will become less active. its no completely bad as long as their thoughts are still intact. if u think they are too lethargic, throw some food in. if they go nuts for food they are most likely ok