Your O's will also upset your decorations, splash water from the tank and may take out your heaters in the process......ain't love grand? They could just be fighting, but in my experience scrapping often is followed by the weaker fish being bullied by the victor, or at least giving him a wide berth. If they start to get down to the business of cleaning off a flat surface (rock, tank bottom) its more than a scrap. Look at their vents; if their breeding tubes start to show, they've got more on their minds than a quick wrestling match. At 4" though they're probably just getting ideas......
As for tankmates, things will be cramped in a 60, and the O's will defend their eggs.