I like to do a prophylactic copper treatment coupled with PraziPro, it covers a good deal of the things you'll encounter and it's relatively easy on fish for a while. I have found that tangs and angles in extended copper treatments tend to develop HLLE. I'm not sure if it's the meds or the lack of a proper reef for grazing and shelter though...
For other ailments like Brook, I prefer to treat on a case by case basis given the toxicity of the treatment.