Ich usually shows up in the first week of a new fish being introduced into a tank.
Do you have any invertebrates, corals, or anemones? Because if you don't I would recommend adding copper or doing hypo-salinity. If you do I would probably just make sure to get him fed good, keep the stress low, and make sure water quality is top notch. In the ocean fish have about a 50/50 fight off rate of ich.
Move the nem to your display tank.
Yea but ill be getting some lights in two weeks so ill have to see if the clown can make it that long