Well this is another confusion I have. Reading articles and thread it says I should not change the bio-bag from my filter because the bacteria. The instructions from the filter(Tetra whisper it came with a kit for a 10g) says I should replace the bag each month. I'm very confuse and I don't know what I'm suppose to do. By the way my tank hasn't finished to cycle yet, already 5 weeks and it in the stage when there is almost no ammonia but nitrites are high.