I am not sure about fishless cycling as i am doing mine with fish in as i didnt know about fishless cycling before i started, thats the reason i am having to do lots of water changes, to make it better for the fish. My cycle has started now and i have ammonia readings of 1.0, so i am doing 2 20% water changes a day so the fish dont get ill. I wouldnt have thought you would need to do any water changes when doing a fishless cycle untill your tank has cycled and you would maybe do it before you add your fish. Its the filter where the bulk of the bacteria will be not the water. I would see what anyone else has to say though as i am no expert. GRJ