Dear Sean:
Yes, sir, it is safe to treat the aquarium while the seahorses and other fish are still present. Fenbendazole (brand name Panacur) is not harmful for the seahorses at the prescribed dosages and will not affect your biological filtration. However, if there is a heavy population of hydroids, Aiptasia rock anemones, and/or bristleworms in the aquarium that’s being treated — as is often the case with tanks that have lots of live rock — there is a distinct possibility that treating the main tank with Panacur will result in a sharp spike in the ammonia and/or nitrite levels due to the mass die off of worms, etc. that results, and for this reason most people will remove their seahorses and delicate invertebrates to a hospital tank while the main tank is being treated.
Since your pregnant male may be delivering a brood of young in the aquarium that you’re considering treating, be sure to use the lower dosage of Panacur recommended for nursery tanks and dwarf seahorse tanks with fry (1/16 tsp. per 10 gallons). As we have discussed before, fenbendazole normally does not harm cleaner shrimp and decorative shrimp at this dose, and with the exception of Astrids (Astrea), Coit and Worden have found it does not usually affect the types of snails typically used as cleanup crews (e.g., Nassarius, Ceriths, and Nerites). It will kill starfish and other echinoderms but copepods, hermit crabs, and shrimp are normally not affected. So as long as your snails are not a species of Astrea, I suspect they will tolerate the treatment with fenbendazole without a problem, but I cannot say that for certain in your case since I’ve never used it on a tank with Margarita snails. Your shrimp and Nassarius snails should tolerate the treatment without a problem and can continue to serve as your cleanup crew.
Regarding your greenwater/copepod tank, why not try using the heat treatment to cleanse it of any hydroids, Sean? A temperature of 92°F shouldn’t be harmful to the microalgae or the copepods, and if that is sufficient to eradicate the dreaded droids in the greenwater tank, then there’s nothing to worry about. If not — if the hydroids survive the heat treatment — then you can always breakdown your greenwater tank, sterilize everything, and start over again from scratch.
As for the biofilter in your spare 10-gallon tank, if hydroids are present they have probably found their way into the filtration system as well. The hydromedusae or miniature jellyfish stage of the hydroids are susceptible to being filtered out, and they are probably entrenched in the biofilter. They will proliferate anywhere where there is a steady supply of copepods, rotifers, our baby brine shrimp, so if you had allot of pods in that aquarium, I wouldn’t be surprised if the hydroids have also infested the biofilter. If you leave the filters and skimmer running while you administer the heat treatment, as described in my previous post, that may eliminate the hydroids from your filter without destroying the beneficial nitrifying bacteria are otherwise compromising the tank.
Best of luck controlling the hydroids and getting your greenwater nursery setup going again free of any hydroids, sir!
Respectfully,
Pete Giwojna
Ocean Rider, Inc. is an Organic Hawaiian-Based Seahorse Aqua-Farm & Aquarium that Follows Strict Good Farming Practices in Raising Seahorses and Other Aquatic Life.
