about four days ago i got a bala shark for my 55 gallon aquarium. He shares the tank with 7 tetras, 8 male guppies, 2 angel fish, a gold fish and a chinese algea eater. Since i've had him he has not eaten anything he does not show even the slightest intrest in the food. He is still active but in the last two days i noticed his fins are turning red. all the other fish are fine. the only other time anything like this has ever happened was when my new angel fish would not eat for like two weeks he started again but then stopped for another couple of weeks and then died. the angel fish was different because the other two angels were charging at him and he would try to eat but would either spit it out or stop right before he put the food in his mouth. So i don't think the angel and the bala have the same problem.i'm feeding the bala tetra min tropical flakes which i have always used on my fish. someone please tell me what's wrong before it's too late!