Okay final word......leave them be, they are sorting out their sexual issues and will be fine. Just make sure you have hiding and areas that the smaller can escape to if necessary. By chance is the smaller one sort of shimmying on his side as this is a classic submissive act by the male to the dominant female. I DO NOT suggest adding any other clowns as 2 is maximum in a tank of this size. I have 4 clowns, 2 ocellaris/percs in the 75g who were added at different times, the smaller male was picked on at first by the larger female but they now spend all their time together. The 2 clarkiis on the other hand were added and never have sorted out issues, they avoid each other for the most part but survive in a 29g together.....