Thank you Tom about such an simple but effective design

I have 2 questions:

1. what is minimum GPH of filter pump for this reactor to effectively work? I have ~50G tank with JBL Cristal Profi 250 external filter ( around 100GPH ).
2. I hear people that they hear noises coming from reactor... is it really noisy? May be noise is only when CO2 is being injected, or noise is from water flow? My aquarium is in bedroom, so it is important for aquarium stuff to work quiet.