I only have a gallon of water in my 10 gallon viv. I don't use a filter. I change my water every 7 to 10 days. If the FBT's aren't liking your water, there is an issue. Have you checked it with one of those aquarium test kits? Possibly it's too alkaline if you are using municipal water from the tap. I use distilled or spring water from Wal-mart.