[APD] daily CO2 swings

[MJPinckard <MJPinckard at lbl_gov>]

I just finished setting up CO2 on my tank (~65 gallons of water).

I'm using an eheim diffusor which came with my regulator.
I positioned it so that the bubbles have to trickle through some plants
and the output flow from my sump is making a downward current
in the same area. This causes the smaller bubbles to travel sideways
for a while before rising to the surface.

In the morning, before lights on, I measure 18 ppm CO2 (6.8 ph 3.5 kh).
In the evening, after 10 hours of lights, CO2 is down to ~7 ppm (7.2 ph, 
3.5 kh).
Lights:
   40 W fluorescent grow bulb on roughly 9 am to 11-12 pm (I turn on/off)
   100 W PCF on timer from 11 am to 9 pm

Other water parameters
   Nitrates (~5-10 ppm, varies)
   PO4 - 0.2 - 0.5 ppm
   GH - 5
   trace - 1 dropper each of Seachem Fluorish and Fluorish with Iron daily

Plants are noticeably growing, but I'm not seeing a lot of pearling (at 
least not
in the evenings when I get home from work and check water parameters).

Couple of questions:

1. Is the 7ppm in the evenings too low?
2. How high is too high in the mornings?
3. Short of throwing away my eheim  and using some other kind of reactor,
   is there anything I can do to increase the efficiency?
4. Should I leave things alone for now?

Maggie
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