That’s ich. There may be other issues, but the spots on the hepatus fins are ich, mucus plugs don’t grow on fins. Also, the emperor angel has the blotchy appearance they show with ich or flukes.@Jay Hemdal @vetteguy53081 @threebuoys
I apologize in advanced hippo is real hard to get a picture of. I added pics of the other fish to check out aswell. Hopefully the setting on the lighting helps.
Jay


