It also depends on the fish. My long horn cow fish doesn't really hide at night, not that he could fit in to any tight spaces anyway. He's about as graceful as as cube van.
At night he just sort of goes in to this weird non-reactive stupor, even though his eyes are still moving around. You could drop his favourite food literally right between his eyes and he wouldn't react to it. He sits right in the middle of the tank just above a colony of SPS for the whole night. He's not the best of swimmers when he's alert, and he really seems to visibly struggle in strong current at night.
I reprogrammed my apex a while back and forgot to add back the night mode, which meant that "tidal swell" mode, which ramps up to all pumps at 100% every couple of hours was running all night. On the third morning of that I woke up to find the cowfish inside one of my overflow boxes. He didn't actually fit so large parts of him were out of the water and he was as close to death as I think I've seen a fish that managed to live. He lost most of his tail and his dorsal fin from that. Since adding back a night mode where everything runs at a seriously reduced power, there hasn't been another incident.
My anthias on the other hand all disappear in to the rocks and wedge themselves in to tight spaces together every night, and my trigger fish has dug a cave so deep you can't see any part of him when he's inside it, so I think I could simulate a hurricane every night and they wouldn't even notice.
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