I agree that it can be tough with all of that live rock, but it will be better for his health in the long run to get him out and treated. Hopefully he can handle the temporary stress. But my lemonpeel wouldn't come out of the rock either. I literally had to slowly lift the piece of rock where I knew he was hiding out of the water so that he would gently fall out and into the tank water, then catch him with a glass viewer instead of a net if you can to reduce stress. This will be easier if you have 2 people as someone can help you. That way one person can gently lift the rock while the other is waiting to get the fish in the viewer/net when he falls out. It will stress him a little but in the long run if you can get him and treat him it will help.