This version is prepared without peppers so that the flavor of the sea dominates. This recipe comes from Bernie Matz of The Cafe at Books & Books, in South Florida. He prefers to use fresh grouper, but striped bass or other firm white fish will work fine. Try not to use a fish that has previously been frozen, they are not as firm. The ceviche will keep, under refrigeration, for 2 days, but eating withing 3 or 4 hours is optimal since he fish will continue to "cook" in the citrus juices.