What kind of filteration do you have? The only thing I can think of is bad water. Usually smell, color and appearance of water is sure signs of imbalanced water perimeters. Have you done recently cheked and done your daily water changes, had all filters working, checked ammonia/nitrate, and PH levels??SteelGluer said:well when i say yellow milk, I meen add some yellow dye to milk thats what it looked like, Ive had aquariums for 20 years now and have never seen anything like it.