I have some old bilge pumps (12V, 500-1000gph) I’d like to be able to use as water circulators/aerators in small (<50gal) tubs. I’d like to try and constrict the flow and add an air injector to enhance aeration. I am working with thick wall 1/2"ID plastic tubing. I plan to buy nozzles or construct them out of plastic or brass.
How would I position/size the air injector to maximize oxygen exchange? My initial idea was to use a needle from a basketball pump, then if the bubbles were not small enough, a jet from a carburetor.