green, cloudy water

[Lizzie]

Hi all. My hubby and i really need help.We have a 72 gallon tank, 15 med. size fish, (mostly aggressive), we have changed the water many times, bought every kind of filter you can name, (last one cost $150.00), but the water goes right back to cloudy and greenish, There is not a lot of algae, we have algae eaters. PLEASE HELP US , THANK YOU, LIZZIE