Help Fish Dieing

[i have crabs]

if you have a qt tank i would put the fish in it and start with the copper,im asuming if you see ich on other fish that ich would be the problem with the angle as well,if you angle is laying on the sand a paraguard dip or freshwater dip would probably do more harm than good at this point and you should say good by unless it can hold out untill some other treatment would start helping.
if you dont have a tank you can copper i would recomend trying
http://www.kentmarine.com/saltwater/rxp.html
i believe its invert and coral frendly.
from the few times ive delt with ich copper is the way to go but you need a tank devoted to qt uses.