Flatworm Exit itself is quite safe to fish and invertebrates. However, the body fluids of flatworms can be toxic to some reef inhabitants when present in a too high concentration. This body fluid is sometimes excreted when flatworms die.

So when you use this product, it is important to do the following first:

  1. Siphon out as many flatworms as possible.
  2. Keep sufficient fresh activated carbon in a canister ready.
  3. Turn off UV, ozone and remove activated carbon. Keep the skimmer turned on.

Do not underestimate the number of flatworms in your system. In a few cases, a significant number of flatworms can be hiding, such as in crevices. Blow in such and any other potential hiding places to blow any flatworm out. For that purpose, you can use a powerhead or a turkey baster. Siphon out those flatworms as well.

Any body fluids released by the dead flatworms in the water has to be reduced further by using about 1 pound of fresh, high quality carbon for every 50 gallons. The carbon needs to be used in a canister with a sufficient forced water flow.

Take sufficient time for treating the tank. That is, do not treat your tank in a hurry. Also, take time to monitor your tank for at least 6 hours after the treatment. It is also wise to have at least 25% water ready for a water change if required.


  1. Add 1 drop for every 4 liters or 1 gallon.  The dropper contains approx. 300 drops (10 ml). The dropper cap holds approx. 90 drops.  So 1 cap full is good for 360 liters or 90 gallons.
  2. Add it in a high flow area of the tank. If you want to treat a refugium only and if it’s volume is too small for using a powerhead, then mixing should be done manually.
  3. Flatworm Stop should begin to work within 30 minutes.  You will notice the flatworms loosing their grip and floating in the water column.
  4. If within 45 minutes no visible death of flatworms occurs, add 50% more.
  5. As soon as the flatworms start to die, commence with the activated carbon to take out any toxic body fluids. Also, see the above given important remarks.
  6. After an hour or so you can turn any UV or ozone on again.