Rats! I’m very sorry to hear that you lost several snails during the treatments with the fenbendazole (brand name Panacur). But thank you for sharing your experiences with the rest of the group, sir — the information you provided certainly will spare others a lot of grief in the future.
With regards to snails and fenbendazole/Panacur, we can now state the following with a high degree of certainty:
Nerites, Ceriths, and Nassarius snails are not affected by the medication and can remain in the aquarium during and after treatment with fenbendazole.
On the other hand, Trochus or turbo snails, Astrea snails, and especially Margarita snails are sensitive to the medication and should be removed from the aquarium until the treatment regimen has been completed and the fenbendazole has been pulled from the aquarium using activated carbon and/or polyfilter pads for chemical filtration. I will amend my instructions for administering fenbendazole accordingly, Sean.
And it’s nice to have more confirmation that the microhermit crabs commonly used for cleanup crews in seahorse tanks are not sensitive to fenbendazole.
At any rate, it’s good to hear that the Panacur did the job with regard to the hydroids, and it tremendously helpful to have more complete information regarding the invertebrates that tolerate the medication well and those that can’t handle it at all.
Best of luck replenishing your snails sanitation engineers, Sean!