So in terms of preventing parasites that target strictly fish from introducing corals and other inverts I see four options
- Use starvation approach - quarantine in separate system for 6 weeks
- Dip corals - not really effective for parasites in question
- Buy from known systems which have quarantine procedures or do not house fish
- Do nothing - perhaps chances are slim to none for introducing such parasites through coral
I think a combination of 1-3 is probably the answer, using case by case bases. Using an isolated frag tank is probably the way to go for #1 as George suggested but it means you'll have to stick to a 6 week purchasing frequency if buying from questionable sources. It also means your frag tank can't have any fish which are handy for housekeeping. Emerald has an interesting approach that deserves more explanation and pictures but I can't imagine maintaining what is essentially multiple pico systems especially when it comes to more sensitive corals.