pond water is thick with green single cell alge...i guess i did throw off my steadily crystal clear water by not filling it with the pond water from the basement pond...fish arent in the pond yet. except i did release my pieco today..lots of food for him. in 2-3 days my water went from gin clear to green mud...and wouldnt you know it. i cant use my U.V because i broke the quartz sleeve. good news is, i called tetrapond and their sending me a new sleeve at no charge, and its not even a covered warranty item....they are the best in customer service. you may remember they sent me a new 1900gph pump, 2 large bags of wheatgerm food, and the sludge tabs as a thank you for my contributions to their site and facebook page when i told them of my 1200gph pump quiting on me. with my experience with Tetra Pond.i would recommend them on their customer service alone. you gotta love a company that looks out for their customers like that!...i found the sleeves on line starting at about $40.00