Water changes really do not FIX the problem it just helps the issue go away for a couple of days or a week and then it will be right back where you started. I call it a band aid fix. Find out what it making your tank do this and the FIX it properly. I have had to learn the hard way and I am not telling you that it should be done this way and I am no chemist thats what I read everything Randy has to say because he is the king when talking chemistry in a marine aquarium and known by all reefers as such. Give me your email and I will direct you to where he can be found where you can ask him direct questions.