ph swing inquiries

[resk]

I've been using co2 for a few months now, and would like to see a 0.0 swing in ph when my lights go off overnight.

Presently I am using a low bubble count to obtain 15ppm of co2 with a KH of 5.

The lights run from about 11am to 10pm

At 10pm the PH is 7.0 respectively

In the morning, the PH is a shocking 6.6 - 6.7

I chose to use the 24/7 method because from what information is available here and the net, this would minimize the swing to about 1.

With a 3 or 4 point swing, I am trying to figure out why, and what I can do outside of buying a "PH Probe"

Should I revert back to using a solenoid to cut off the co2 along with the lights at 10pm ?

[Kagh't]

if your using CO2 throughout the night, thats your problem. during the day, the plants take up CO2, keeping a balance, but during the night they produce CO2 through respiration, so your pH will drop because there is more CO2 present.

[RTR]

Reminder: Keep your units straight. A drop from 7.0 to 6.6-6.7 is a drop of 0.3-0.4, and is in no way shocking to the fish or plants over a 13-hour period, or at most a drop of 0.031 per hour. If you did the same drop in a few seconds by adding acid, you might see responces.