Welcome to the world of algea bloom. Kristi has been taking care of our fish tank for the past 10 years and has had success with the fish population. Recently we noticed our water was green and foggy. We tried 3 water changes. First change was 2/3 second 1/3 and 3rd time was 1/2 the water. 3 days later the bloom returned. So we started doing some online research on this problem and came across this product. So here is the video review on the Aquatop UVP-13 UV fish tank filter system. I think this is a great product as shown in this video. Enjoy!