If you physically remove as many as possible by siphon, then add any or all of the following.
1. The blue velvet nudibranch ( this is the most problematic of all of the solutions, I have tried them with little success. They go into overflow, they get turned into minced meat in power heads and depending on the size of your tank and severity of the break out of flat worms, it could take a small army of them to do the job and they are not supper cheap. The last problem, is that there entire diet consist of flat worms, that’s it, nothing else so when there food supply is eradicated, you will need to remove them and find then a flat worm infested home, or they will die.
2. As calvin415 has pointed out and was nice enough to supply a pic of, the green target mandarin goby (Synchiropus picturatus) not the blue mandarin goby (Synchiropus splendidus) do an excellent job of eradicating small numbers of worms is tank up to 125-150 gallon were beyond that more fish are required.
3. Any wrasse in the Pseudocheilinus family; They are referred to as having (micro vision) and these fish will devour the flat worms and service your clams for parasitic snails as well, they are very beneficial. This family includes but is limited to the secretive wrasse (Pseudocheilinus evanidus), sixline wrasse (Pseudocheilinus hexataenia), eightline wrasse (Pseudocheilinus octoaenia), fourline wrasse (Pseudocheilinus tetrataenia) extra.
4. The yellow or golden “coris wrasse†(Halichoeres chrysus) is also a great reef inhabitant and a mighty destroyer of flat worms.
5. Then as a last resort, the chemical genocide of (flat worm exit) from Salifert. This will not only kill the flat worms but can also kill many desirable inverts in your system. You need to be there with carbon and water change water ready to go to detoxify the tank from the dieing worms. Also, it DOES NOT KILL THE EGGS, so they will be back and every following treatment even at higher doses will be less effective as the worms develop an immunity.
This is not, nor was it intended to be a complete and comprehensive list or way to eradicate flat worms, merely a suggestion of some common, affordable and easy ways to help with the problem.
Good luck and good hunting,
Scott
