Fish Story

In the seemingly never-ending saga of my battle against the dreaded camallanus worm nematodes infesting my tropical fish, the story continues.

Thanks to a certain big-box pet store located near my home, I imported this “aquarist’s worst nightmare” along with some black mollies I purchased back in March of this year. The time required for the worms to appear is longer than the typical quarantine period, so the nematodes passed into the display tank, unknown to me.

The nematode spawn gets distributed through the water, so they can be transferred from tank to tank by nets and such. The typical cure, a substance known as levamisole, is incredibly difficult to find in the US. Another substance designed for fighting these worms is only available in Europe. I’d love to have some Sera Nematol from Europe but I have not been able to find a dealer for it in the US. We fall back to using PraziPro brand praziquantal.

Fast forward several months, I had the plan to isolate the 1st-generation mollies to a 10-gallon tank, since it seemed the 2nd-generation fish were clean. All was going according to plan and a final dose of medication given to the display tank completed. Then I discovered a worm in a 2nd-generation fish. You only notice the worms when they grow large enough that they are too large to fit completely inside the fish’s intestines and they protrude from the vent.

I quickly moved the fish to the 10-gallon tank and decided that the only way to eliminate the problem would be to euthanize everything. It was a painful decision that brought protests from the kids and wife, and would have been difficult emotionally to perform. I was set to do this in the days before Thanksgiving, to the tune of almost 50 fish.

Last night, I observed this 2nd-generation molly with the nematode nearly all the way out of the fish, which means the fish was passing the worm. I went to fetch my plastic box to capture the fish so I could sedate it and remove the worm for microscope inspection. Determining whether the worm is alive or dead is simple with a microscope because the live worms have a lot of motion inside their bodies.

Unfortunately, in the 20 seconds it took to get the box, the worm disappeared. A loud splash occurred when I walked back into the room, so I suspect another fish ate the worm. If it was dead, no big deal. Alive, it just spreads the problem even more.

However, since I could not inspect the worm, I do not know whether it was alive or dead. That means the fish have won some time as I observe for more evidence that the problem is still with me. Meanwhile, I continue to treat the tanks trying to cure the problem and save the fish.