HELP!!! Dwc help, sharing a pump? Size of container?

my grow box is (21x21x48in) very small yes needing the most out of it here check out my box



Thinking of a 20q sterility container that is 18 1/2x12x11 1/2 inch box so it's the height of a two gallon with the amount of water of a 3.5 gallon bucket?? I could fit either two avg or 8 small sized plants I originally wanted to grow autos but I've been told to go photo in my spacing and I have a 40gallon top fin air pump with brass splitter, splitting the air down two tubes for two buckets no buying multiple pumps or a pump with dual ports did I make an ok descision?
 
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