Do a couple (3-4) of those 20 gal
water changes over the week or so. The new SW
should be well aged/aerated a day ahead of time. It will help reduce the DOC
and help alleviate the baterial issue. Your tank is fairly well stocked so you need to keep an eye on the water quality pretty good. It does not take much for an otherwise easily cured problem to become a nightmare.
As well be sure to use properly fortified foods. If available get some Selcon or Zoecon which is high in [acronym="Highly Unsaturated Fatty Acid"]HUFA
[/acronym]/lipids and will aid the fish's natural immune system. Ensure the foods fed are a good variety of meat and <<vegetable matter