Hello Sofia
We have done both of these things in our lab at various points; using the white (6500K) LED at low intensity so support cyanobacteria growth, and also using CO2 to pump through the headspace. In the later we got a manual flow valve and connected it to a CO2 cylinder with pressure regulator and set it to some small flow rate (e.g. 0.1L per minute) which seemed to work OK. This was then just plugged into the top of each reactor.
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