hi my fan tail had a yellow head iv had him about 6 months now and he has never had one before and i dont think its his colering its raised offa his head but not like a cotten look. the Ammonia was realy high it was at 2 but i did a pronto water change and it is now at 0 the Ammonia was high fore anout 2 and a half weeks i was away and i have a bad roomy hoo fed him WAY to much. i have a 27 gallon tank with 2 dojos in it, the water temp is usaly around 76 to 78 i feed him a wide arange of stuff frum pelates to flakes to fresh food to blood worms. the tank is cycled and has lots of alge. its been runing for about 7 months. he hasnt been acting strange a hole lot he hides alot now and his breathing looks forced not raped or quick. the yellow stops at his gills but there is a exstra bit of skin growing on his gils almoast like an exstenchion of the gills but it dosnt look like it belongs there. i have a good filter in my tank its a biofilter and before i left i cleaned the tank spotless but i only used water and some aquarium salt to clean it . i change the water about 20% a week with non treated water i just let the tap water sit out 4 a few days.if some one could help it would meen soo much thanx