I have five fancy goldfish in a 55 gallon tank. I have been reading mixed recomendations on how often I should be doing 20% water changes. The water in the tank is mostly clear, but is slightly hazy. You can only tell if you stand at least ten feet from the tank. I have several large HOB filters on it, which all have lots of beneficial bacteria in them. I have been doing ten gallon water changes every week in the tank, but should I be doing ten gallon water changes twice a week or just stick with that once a week?