+1 on RD's comments. I co-wrote a publication in Limnology and Oceanography regarding Cu and Fe in the Ocean. Cu, along with many other elements found in fish food (and vegetables as well) have an acceptable range in concentration that is beneficial to each organism. I was actually able to negatively effect some phytoplankton by decreasing the Cu concentration to very low levels. Trace amounts of Cu found in fish foods (and fresh or blanched veggies) are not enough to raise the concentration above levels that are detrimental to anything in your tank.
As for fresh veggies, I am sure that some of the coral foods that I have tried are, in part, veggie juice. IMO, just because lettuce is not found in the ocean, doesn't mean it isn't good for your fish or corals. Nutritional content may be just fine, but the companies selling you stuff would have you believe otherwise
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Dan