Discus water changes

Question
I have kept saltwater tanks for many years with great success.  I am interested in starting a discus tank but the quantity of water changes concerns me.  I have a cistern whch two residences use and cannot be changing 20-50 % of the tank water a week.  The tank setup will be:
125 gallon tank, light layer of gravel, wet/dry filter for biological filtration with a 500 gph pump and a 300 gph  cannister filter for mechanical/chemical filtration.  The tank load would be six large discus, a small school of cardinal tetras and a few cory cats.  Is this enough filtration for this tank with me doing a 5 gallon water change per week?
Thanks, Chris Delaney

Answer
Hi Chris,
  In my opinion, a 5 gallon water change per week will simply not be enough to maintain the kind of water quality you need for discus.  For instance, I have a 155 gallon tank similar to what you describe and I change about 20-25 gallons per week and that is about the minimum.  If I do less than that, the water quality rapidly deteriorates.  

  I think 50% is overkill but 15-20% is necessary, regardless of the kind of filtration you have.

-- Ron
  rcoleman@cichlidresearch.com
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