Not a great pic for a positive ID, but that would be coming out of my tank. Resembles the ones I have pulled out of my tanks that were munching down on my zoanthids.
You're going to have to look for the Nudi's eggs as well, typically they are spiral in shape. Manually remove any eggs you find. with a q-tip. Dips have no notable affect on Zoanthid Eating Nudibranch eggs.