Okay, sir, it sounds like everything went very well during a regimen of Panacur — not even a blip in the ammonia or nitrite levels. Well done!
I agree about your sanitation engineers, Sean — heavy on the snails and light on the microhermit crabs is usually the best way to go.
As for the snails, the only specimens that I know are sensitive to the fenbendazole/Panacur are the Astraea species. Snails that should not be bothered by any residual fenbendazole that’s leached from the live rock include Nassarius, Ceriths and Nerites. Snails that belong to those genera are known to tolerate fenbendazole, so they can compromise the bulk of your cleanup crew.
Feel free to try other snails species as well. The amount of fenbendazole that is leached out of the live rock is relatively small, and I suspect that most snails will handle it well. But other than the types I have mentioned above specifically, proceed with caution when you are experimenting. Get one snail of each type and use them as test subjects. If they survive the residual fenbendazole that is leached from the live rocks for a reasonable period of time, then you’ll know it’s safe to load up on some more of those snails. If not, well, at least it was only one of the snails that was sacrificed. (If you do experimental long those lines, sir, please let us know the results.)
As for the crabs, hermits don’t seem to mind fenbendazole bit. Personally, as aquarium janitors and scavengers, I like a combination of Dwarf Blue-leg (Clibanarius tricolor), Left-handed (Calcinus laevimanus), Mexican Red Legged Hermits (Clibanarius digueti) and above all, Scarlet Reef hermit crabs (Paguristes cadenati), which are my personal favorites. As you know, it’s very important to obtain dwarf war microhermit crabs for a seahorse tank — species that start out small and remain small even when they reach their maximum size, such as the species mentioned above.
The Scarlet Reef Hermit Crab (Paguristes cadenati) is a colorful micro-hermit that’s a harmless herbivore. So cannibalism isn’t a concern at all for these fellows, nor are they likely to develop a taste for escargot. As hermits go, most of the time the Scarlet Reefs are perfect little gentleman and attractive to boot. I even use them in my dwarf seahorse tanks. Best of all, they eat all kinds of algae, including nuisance algae such as red, green and brown slimes, as well as green hair algae.
If you’re going to have any hermits, stick with species like the above, which are known as micro hermits because they start out tiny and stay small. Avoid Anomura species of hermit crabs no matter how small they are, however, because they will kill Astraea snails to obtain their shells.
A mixture of the snails and micro hermits we have discussed will provide a very good balance of herbivores, omnivores, and detritivores that are all active scavengers and completely compatible with seahorses. They will clean up meatier leftovers such as frozen Mysis as well as helping to control nuisance algae.
With regard to the hermit crabs, there are a couple of other possible risks you should be aware of aside from the possibilities that the hermits could grow a large enough to be a threat to the seahorses.
For example, sometimes it works the other way around. Micro-hermit crabs are generally entertaining additions to an aquarium that do a great job as scavengers and get along great with seahorses, but over the years, I’ve had a few seahorses that were confirmed crab killers. These particular ponies were persistent hermit crab predators that specialized in plucking the hermits out of their shells and attacking their soft, unprotected abdomens, and they honed their skullduggery to a fine art. They were experts at extricating the crabs and would eat only their fleshy abdomens and discard the rest. Mind you, that was only a few individuals out of a great many Hippocampines, but I could never keep hermit crabs in the same tank with those specific seahorses.
On the other hand, sometimes it’s the micro-hermits that are the troublemakers. Most of the time, they coexist perfectly well with their fellow janitors in the cleanup crew. But I’ve had more than a few tiny hermits with a taste for escargot that persecuted snails mercilessly. These cold-blooded little assassins would kill the snails in order to appropriate their shells. Once they had dined on the former occupant, they would take up residence in their victim’s cleaned-out shell! It soon became clear that these killer crabs were driven not by hunger, but by the need for a new domicile. Once I realized they were house-hunting, I found I could curb their depredations but providing an assortment of small, empty seashells for the hermits to use. Colorful Nerite shells are ideal for this.
Best of luck building up a solid crew of sanitation engineers for your new seahorse tank, Sean! Here’s hoping you soon have a brood of healthy babies on your hands, sir.