Guide to AEFW

Posted on June 27, 2012 | 0 comments

Acropora Eating Flatworms or AEFW are flatworms who live as parasites on Acropora corals. In my experiences at least two different types of flatworm seem to affect our Acroporids although others probably exist. I’m not sure if the two types I have dealt with are two different species, or the same species exhibiting two different types of behavior. Of these two types, one seems to be a rather benign species that seems to do harm only when present in large numbers. This flatworm acts as an irritant and the corals hosting it keep their polyps withdrawn a majority of the time. I have never observed any tissue recession, bite marks or egg masses with this particular flatworm. On the other hand there are the larger, more aggressive AEFW that produce a lot of egg clusters and tend to consume the Acropora until it starts to STN at the base caused by stress.

To my knowledge, no in-tank treatment exists that positively eliminates these flatworms and harms nothing else. Various fish have been tried as natural controls with varying degrees of success. I’ve added different types of wrasses to infected systems, but I’ve never seen a 100% removal of the flatworms. If a biological control is what you seek, try wrasses from the genera Halichoeres, Psuedocheilinus or other small wrasses. Many times biological controls can keep a predator or pest population in check, but cannot eliminate them completely. To completely eliminate the AEFW infection, an out of tank dipping treatment is necessary.

The procedure I described have been successful for several times for me. Unfortunately I didn’t learn from my mistakes and didn’t set up a quarantine tank. That’s why I got infected again.

The treatment procedure:

This procedure is based on an out of tank treatment with Levamisole. Levamisole is available through your local vet of on the Internet. When you explain the purpose of use most vets won’t give you a hard time and subscribe the medication.

Set up a quarantine tank with decent flow, light and heating. Other equipment isn’t necessary because waterchanges (with tankwater!) can be done once or twice a week to keep the parameters in check. Goal is to treat the corals with 50 ppm of Levamisole for 4 hours. This have to be repeated every week for four weeks.


AEFW egg clusters. (photo and featured photo by J. Weatherson)


To calculate drug dose use the following formula:

For 100% active drug:

volume in liters of tank x ppm (drug dosage) / 1000mg/g=#of grams required of the drug

For drugs that have less than 100% active drug, you take the percentage of the active drug (Levamisole hydrochloride is 80% active w/ 20% inert ingredients) and multiply the percentage to the 1000mg/g. So…

volume in L x ppm / 800mg/g = grams of drug

So if your treating a 10 gal tank w/ 40ppm Levamisole it is:

37.8L x 40ppm / 800mg/g= 1.89g of Levamisole

  1. Calculate the amount of Levamisole you need for the treatment tank to bring the concentration Levamisole to 40 ppm.
  2. Add the Levamisole to the treatment tank and check the corals regularly for their condition.
  3. After 4 hours, gently blow off the corals to remove any possible attached AEFW. Use a small powerhead for this.
  4. Inspect all the corals very well for egg clusters, and scrape them off.
  5. Empty the tank with treatment water and clean it out very well.
  6. Fill the tank with fresh aquarium water, to prevent further stress, and place the corals back.
  7. Repeat weekly, four times until no AEFW or eggs are found anymore.


Corals during treatment

One way to ensure that these predators never get into your display tank (again) is the one thing that is rarely done: quarantine. Many aquarists have the mistaken idea that you have to spend a lot of money on an elaborate quarantine system. A quarantine system can be a simple 20-gallon tank with a powerhead and a dual PC bulb or T5 bulb. Use water from your display tank for initial setup and water changes. Keep the coral in quarantine for at least a week. During this quarantine period do a couple of investigative dips with your dip of choice. I would suggest to use Coral Clean Revive because in my experience it is a lot less aggressive towards the corals then Iodine-based dips (like TMPCC). A close inspection with a magnifying glass can also expose some unwanted guests.


Corals after treatment in Quarantine tank

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