ok.. i have been changing the water daily.. at least 50% sometimes 75%. i treat the water prior to adding it.. the water is at temperature.. now for the last two days the nitrites have been spiking up to 2.0 after the water change and 5.0 prior to change. i have been having it go to 0.0 after water changes.. why is it now only coming down to 2.0? is this normal? don't know what to do other than water changes daily.. now the nitrates are at 20 and the ammonia is at 0.0 and has been now for almost 2 weeks. help