Dear Carrie:
It sounds to me like some of the dwarf seahorse fry were definitely premature and that you’re having a problem with hydroids — a double whammy for the poor little guys!!! If that’s the case, they never really had much of a chance…
If you want to avoid treatment with fenbendazole (Panacur), hydroids of most kinds can be eradicated from the aquarium by raising the water temperature to 92°F or above for period of 3-5 days. Keep all of the filters and equipment operating so that the hot water circulates throughout them and destroys any hydroids or hydromedusae that may be present in the filtration system. (Seahorses and their tankmates, including snails and the cleanup crew, must be removed to a temporary holding tank while the heat treatment is carried out.) Maintaining the water temperature at 92° for this period does not harm the beneficial nitrifying bacteria in your biofilter, injure marine plants or macroalgae, or kill off copepods and other beneficial microfauna.
After the treatment period, perform a large water change to assure that the die off of hydroids does not degrade your water quality, and adjust the water temperature back to normal, and all the animals can be returned to the aquarium. The tank will not undergo a "mini cycle" and there will be no ammonia or nitrite spikes.
However, not all types of hydroids respond to the heat treatment method of eradication. The snowflake type of hydroids that are all too common seem to have no difficulty surviving the heat treatment. So generally speaking, then Panacur is a more reliable way to eliminate them. Some folks might describe the snowflake type of hydroids as "fuzzy starfish," in which case the heat treatment may not be effective.
Likewise, a good way to prevent hydroids from becoming a problem with dwarf seahorses is to set up and establish two dwarf seahorse tanks simultaneously, one of which will house the dwarf seahorses and one of which will serve as a backup tank for the inevitable day when an outbreak of hydroids occurs. That way when hydroids appear on the seahorse tank, the ponies can simply be transferred to the backup tank without missing a beat, and the tank with the hydroids can be cleansed of them using the heat treatment and become the new backup tank. It can then be held in reserve, fully cycled and ready to go, the next time hydroids appear in the dwarf tank. There is an excellent discussion of this method of hydroid control in Alisa Abbott’s guidebook (Complete Guide to Dwarf Seahorses in the Aquarium).
Best of luck eradicating the dreaded ‘droids, Carrie!
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.
