Hi all I have 3 Congo Tetras I have had them for 2 years now they are with a community of tropical fish Discus etc in a 5ft tank but what I see with them now the 3 of them are facing the back of the tank and at the top of the water where before they were always swimming side to side across the length of the tank they don't seem to eat now to. All my Tests of the water are Normal. Also all the other fish in the tank are great. Can any one tell me what could be wrong if anything. Thanking you all Peter.