i have a 55 ltr planted aquarium with pressurised co2, drop checker is at a healthy lime green colour in the day while diffusing co2. I noticed my ember tetras nipping up at the surface (a clear sign of shortage of oxygen in the water) would it be safe to run the venturi valve on my powerhead at night when the co2 is off? or would this cause too much of a fluctuation in the water ph and cause an algae bloom?