Ask yourself this, is the CO2 dissolving when the powerhead is off?
The DIY CO2 will still go into the reactor, but it'll simply escape out the burp tube.

When the powerhead is on, the reactor will start dissolving CO2.
You can also set a timer for the CO2 to come on 30 min prior to lights on and 1-2 hour or so before they go out.

Regards,
Tom Barr