How long to Quarantine corals for?

[Aquattro]

A good visual inspection will often suffice, depending on the type of coral in question. Some people dip in lugol's iodine for a few minutes, Wendell recommends epsom salts as a dip. Check for bugs, flatworms, nudibranchs, etc with a magnifying glass. If it looks clean, it probably is.
The problem with a Q tank for corals is duplicating the lighting and water quality required for any length of time.