Melafix Marine has a recommended formula for coral dipping on the back of the bottle. Pretty sure it's 20 mL per 1/2 gal and for only 5 minutes. I've successfully used a solution 1/2 that strong for 15-20 minutes. Nice thing about Melafix is my corals don't slime or seem stressed at all (fluke tabs tended to make the corals slime pretty bad). Melafix won't kill Acro Eating Flatworm eggs though, you need to check corals closely for eggs if you see any flat worms (dip in a white container so you can see what comes off the corals).
I don't think Melafix will take care of red bugs, i check new frags with magnifying glass or scope and add interceptor to the dip if I see any red bugs.