1Thinly slice each scallop & place in a medium bowl. Add orange, lime juices apple cider vinegar & grapefruit bitters (if using). Make sure that all of the scallops are fully submerged, then covered & refrigerate for at least 12 hours or, even better, overnight.
2rior to serving, peel & segment grapefruit, oranges & lime. (You need to use a knife when peeling lime.) Slice each segment into bite size pieces. Place in another medium bowl. Add red onion, chili pepper (if using) & cilantro. Strain scallops & discard marinade. Add scallops to sliced citrus mixture; toss well to combine. Divide among chilled bowls or glasses & garnish each with a few tortilla chips.