It may depend on what your keeping.
I've QTd frags in a tank that used to have copper and they did fine after rinsing things. However, astrea snails didn't last a week and an emerald crab died after a few weeks.
I later had ammonia problems in that tank when I put too many fish in too quickly, so I can't rule out ammonia instead of copper as the culprit. But I can verify that at least some coral frags do fine with whatever residual copper equipment might have after a thorough rinsing.
My corals were bird's nest, monti shelf, duncan, candy cane, favias, zoas and a kenya tree.