Another option - and it's what I've switched over too - is to buy all properly quarantined fish.
I treated all my tanks with API GC & Selcon soaked food for 2 weeks - I knew I had some internal parasite as I had a yellow tang that was eating great but getting skinnier.
Since then - I've purchased fully quarantined fish and I have to say I've had great luck so far. I'm pretty confident that I have disease free tanks at this point.
FWIW every tank I have has gone through 75+ days of being fish fallow at some point in time
Can it be more expensive ? yep - but not as much as you would think. Plus the personal level of service you get from someone that really cares about the animals they are selling you is great.
For reference - I paid $253 for a medium hippo tang, 2 large yellow tailed blue damsels and 3 pajama cardinals - that cost included shipping and I was in fairly constant contact with the seller.
He's currently quarantining a couple more fish for me.