About Pesky Hydroids in a dwarf sh tank, I had to use panacur bought from seahorse source, I used the liquid.. but you can`t put much of anything else in the tank. nass snails survived also the live rock and sand cannot be used in any reef tank, the panacur stays in the rock for yrs. Caribbean learchis poica , Feeds on the stinging hydroid pennaria distichia very much helps remove these unwanted tank pests.. purchased from cramers critters for $2.50.. I have never tried the Nudibranch ..