i just bought a fluval fx5 for my 150 gallon oscar tank. i dont really understand the types of filtration to put in the three layers that are in the canster. can anyone help me out with what to buy? i have 1inch bio balls in the top center right now but what else, i have no idea what to use. the fish are about 7 inches each and i have 4 of them. i still have to buy the sponges that go around each layer but i dont know what to put in the center. thanks in advance.
