I have answered this question at least 50 times in different threads so I decided to post directions here.
Zoa eating nudibranch happens! Eggs can come on a frag and within a week you can have quite the infestation. There's no need to panic about them, because it's very simple to eradicate these nasty boogers from your system. All you need to do is use salifert flatworm exit and they will disappear completely within 2 weeks. The nudibranch matures in 5 days and starts to lay eggs. The trick is to kill them before they start to lay eggs. The only variation to the original instructions is the dose. You need to dose one drop per 3/4 of a gallon. So 12.5 drops per 10 gallons of total system volume. This means of your tank is a 100 tank with 100 lbs of live rock you still treat it as 100 gallons and put 125 drops in the tank. The first dose you will more than likely see some flatworms floating around in the tank. If you can actually see any zoa eating nudibranch in the tank keep an eye on them and watch them die. If you witness one die then the rest will follow soon after. If you start to see the flatworms die wait about 15 minutes and start using carbon. When flatworms die they produce a very strong toxin that can and will harm all the livestock in your tank. Don't underestimate how toxic this can be! Make sure you're using a large amount of carbon to remove all the toxin. The directions will include that part and need to be followed closely. You repeat this process every 72 hours for 4 total treatments. At this point all the eggs will have hatched and they will have never laid eggs because they were never adults.
I have used this method twice and completely eradicated zoa eating nudibranch both times. Other reefers have often used this process and had the exact same result.
