Oscar cichlid problem

[fishstix]

Hey, im starting a freshwater aquarium as a school project with my bio teacher. We've got a 55 gallon tank with 4 sucker fish, 3 tiger barbs, 2 goldfish, and one oscar cichlid. The ph is 7.6 and the ammonia levels are at .25. I had the temperature at about 82, but i read that oscars need it at 72-77 and just recently lowered it. The oscar is albino, so i made it a small cave out of bricks from my backyard (dont worry, i cloroxed the bricks then covered them in bacteria supplement before putting them in the tank) to protect it from bright lights, but it seems that the light isnt really the problem. He all he does is lie tilted underneath a small bridge structure in the tank. I added some bacteria supplement to attempt to lower the ammonia levels and im concerned that i need to lower my ph as well. Does anybody have the same problem with thier oscar cichlid? He wont swim up to the top of the tank to eat the pellet food i got him, so ive just been giving him flake food. Im considering buying a number of brine shimp and hoping that he will eat those, but i just dont know what is up with him.