i had 4 goldfish in my tank previously for about a year now.i thought about adding some other fish and bought three koi and two angelfish.an angelfish died the very next day of i don't know what cause.and a koi also died.and my healthy goldies also seem to be ill.i guess they have itch as they are scratching.im very tense as i had them healthy for a whole year and i don't wanna lose any of my fish.and also the angel fish isn't eating ANYTHING AT ALL.it just stays in a corner and whenever i put something for her to feed the other fish eat it.angel is very small about one square inch and the goldies and koi are large.i tried keeping the angel in a separate bowl but it didn't eat anything there too.PLEASE HELP ME I LOVE MY FISH TOO MUCH AND I DON'T WANNA LOSE ANY OF THEM.PLEASE.