Look at the diseased fish thread at the top of this forum, there are pictures of different fish with different diseases. It does sound like ich! Try not to use copper as a treatment, as you will never get it out of your tank, and it will kill invertebrates or corals that you have now or in the future! Also, it is probably stressed being in a 55 gallon tank. It will grow to about 10 inches in length, and it has to have a minimum of 100 gallons to thrive!