The replacement bulb is on the way , so I hope I don't need to replace the whole fixture . Well over the weekend I lost 4 horses and water is PERFECT sg 1.019 , ammonia 0 ,nitrite 0 , nitrate 0 , and ph 8.2 . So my guess is not enough food especially since in the begging they went almost a week without food so I have upped to 3-4 feedings a day.