The tower on my trickle filter has two ports 1 for Co2 1 for o2. 30 minutes before the lights go out Co2 is shut off. 5 minutes after the lights go out. an air pump comes on repressurizing the chamber with air. 35 minutes before the lights come back up the pump shuts down, and 5 minutes later Co2 is re-pressurized. Pure o2 is useful for heavily planted systems, and high altitude though. (Folks always seem to miss the part about altitude ???) The tower does function in a Hyperbaric capacity, but I have noticed some stress crazing at a few joints. There is an obvious 1 1/2" difference in water line when pressurized. Isn't Duct Tape just the greatest ? I'll be switching to tanked O2 just as soon as my wife drops her guard ! The only real problem suffered so far is that everything in the tank is breeding with the occasional aggression that goes along with that, and We remove 1/2 a 5 gal. bucket in plant trimmings each week from a wee 65 gal. tank.

The very same could be applied to Co2 reactors, and inline Co2 reactors. Whether it's gassing or degassing fluid the results are the same, just depends on the gas introduced right ?

Whether you add a port to a trickle filter, or add an inline venturi to the output line of your canister. Most of us already have an old air pump laying around and already use timers.