I have a 75 gallon tank. It has been set up for about a year with 2 Marineland Emperor 400 HOB filters on it. My tank is stocked with the following: 10 neon tetra, 8 glowfish, 4 black mollies, 4 albino cory. My tank keeps getting dirty very quickly. After I clean the glass, do a water change and vacuum the gravel it looks like the attached pictures in about a week. The plants and decorations I have washed at one point and last month I replaced all the plants since they were looking bad. They are artificial plants. Do I need better filtration? I have friends that their tanks look clear and no issues but they have more filtration. Any suggestions?