So the past two days I've noticed my male GBR has been hiding away in the corner of my tank and has been popping out every now and then but stays near the corner. He has also gotten alot skinner, which made me believe he isn't eating. After spending a good amount of time watching him I realised that his mouth doesn't seem to open. I have watched him try eat the food but he just swims into the food and his mouth doesn't open. Now I know he isn't being bullied or anything from what I can see or know of his temperament, which made me believe that either a change in water parameter's has had this effect on him or he has developed some type of fungus which won't let him open his mouth. I will be checking my parameters tomorrow and plan on doing a 50% water change just to be on the safe side. I will also be restocking the tank with new substrate and plants which hopefully might change his surroundings. Any idea what this can possibly be? I can go buy medication etc if needed, I don't want to lose him! He has paired up with a female and have high hopes for them! Cheers EDIT: It seems like it could be fungus, after taking a closer look by netting him I can see bits floating off his mouth. I have done a 25% water change, increased the water temp and I have added protozin. Any other advice?