Is this accurate info? Daveks told me this. I decided to consult your wisdom to double check. Thanks! (You can check my journal for the whole thing)
in a 4ft by 18” tank, especially with a 20” water column height you’ll need that spraybar blowing down back wall to make current at back of tank that sweeps down and across substrate and keeps debris moving and then 2 nozzles in top corners blowing slightly towards center and providing surface ripple and the current will meet in middle and then sweeps down front glass to provide circulation to front of tank.
I would have at least that many outputs splitting up that 560gph into 3 185gph outputs and distributing them around tank evenly front and back.
With that segmented spraybar you might be able to get away with pointing half of it down back wall behind plants and then point other half up at front glass and give the front half of tank circulation and do surface ripple/gas exchange.