How much flow is too much flow?

[Fishward]

Hey,
I am fairly new to marine tanks and i just set up a 30g hex tank. im curious what sort of flow is considered substantial and what amount is considered low? I currently dont have any powerheads, but my return pump from my sump is rated for about 1000l/h (200G/h) at the height difference ive got going now. is that enough circulation for a 30 gallon tank? should i get a powerhead to supplement if i want to keep corals?