In my very long experience as an aquarist, I have encountered, like many of you, all kinds of pests that can dishearten even the most tenacious enthusiast. They are mostly spontaneous or accidentally introduced organisms, which, growing and reproducing, can really cause a lot of problems.

One of them is Oenone Fulgida, a worm of the Polychaeta family, which can reach remarkable dimensions (the one I had was around 50-60 cm).


How to recognize its presence in the tank:

Unfortunately, it is quite simple. The Oenone Fulgida worm feeds on molluscs and bivalves, so if you notice slugs, tridacnas and similar organisms quickly disappearing, there is a good chance that this worm is the culprit. To be 100% sure, just check if on the dead or dying tridacna there is the unmistakable transparent gelatinous mucus that the worm secretes to suffocate its pray, to then take its time eating them. If you find this mucus, then you can be sure that you have an Oenone Fulgida in your tank.

How to catch it:

Reading on forums and blogs on the internet, I found something that was right for me. To build a really effective trap, you will only need a few and easy to find things.


  1. A PVC tube, about 20-25 cm in length and with a diameter of 25 mm.
  2. 2 PVC spherical caps with a diameter of 25 mm.
  3. A nylon sock of the kind used for activated carbon.
  4. Some sturdy fishing line, not less that 0,16.
  5. (Optional) Toy night vision goggles, which can be bought for about 20 euros.
  6. A drill to make holes in the PVC.

First, take the fishing line and make a noose, or if you prefer, a slip knot. If you do not know how to do this, you can find many guides on the internet, and it is very simple.


Take the PVC tube and use the drill to make a small hole close to one of the extremities.


Then make the nylon thread with the noose that we prepared earlier pass through the hole.


Take the drill again, and make a hole in one of the spherical caps with an 8mm drill bit. The cap with the hole will be the one to be placed at the extremity of the tube where you drilled a hole for the thread.


Now make the sock go through the noose and into the tube.


Then close the bottom of the tube with the cap without the hole, put the bait in the sock (as deep as possible) and close the entrance with the cap with the hole, letting the edge of the sock come out of the tube.



The trap is ready to be used.


The hunt:

Oenone Fulgida only comes out at night, and to catch it it will have to be completely dark in both the tank and the room. To help with this, I bought online for a few euros some toy night vision goggles, which are perfect for this purpose.


As a bait I recommend to use a piece of sardine, because not only it is very desirable to all the inhabitants of the tank, but it also releases a very strong smell that will lure out the worm in no time.

Place the trap horizontally on the sand, with the hole facing the worm’s hideout (if you know where it is). It has to be easy to retrieve, so think carefully about its position. About an hour after the lights have been turned off, check with the goggles if the worm’s front part is inside the trap.

Always give the worm time to slide all the way inside the trap to have more chances of succeeding. Wear rubber or latex gloves and do not touch the worm with your bare hands.

When you are sure that the worm is inside the trap, pull the thread. Do not use too much force, or you will risk cutting the worm and therefore multiplying the problem. When you pull the thread, the noose will close around the sock and the worm, stopping it from sliding backwards and breaking itself.

Now take the tube and pull gently, making the rest of the body of the worm come out of its hideout, always being careful not to break it.

Once you have pulled it out, you should have the trap in your hand with the worm hanging from it.




This is my experience and I can assure you that for me it worked perfectly.

I hope this guide can help all the aquarists that are being vexed by this worm, and give hope to those who had given up, thinking there was nothing they could do to get rid of it anymore.

 Lorenzo Dainelli