the main point here is that tangs, when observed in the wild, eat constantly. they will pick at different types of algae almost non-stop all day long. this means that they have a varied diet consisting of different algae and whatever small fauna lives in the algae. therefore, varied diet is a must in captivity. many different dried, fresh, and prepared seaweeds are available, and they are fairly inexpensive at certain grocery stores. the occasional romaine lettuce probably will not hurt anything, but mainly the diet should consist of these varied seaweeds. and more liverock is almost always better.