That is not too much flow. You have about 51 times turnover, personally i have more.
There is way more flow in the ocean than we can replicate in our tanks. Flow does not kill fish.
I would say your buying too small of fish if they are getting sucked in repeatedly. Or as stated something else is wrong and the fish are weak.
Im not sure how else a yellow and sailfin tang would get caught in a powerhead unless they are only like 1-2" maybe.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.