Jellyfish thriving in my tank....? *PICS added on PG03*

[leliataylor]

They are hydroids. If you want them to proliferate add some newly hatched baby brine shrimp, you will get a population explosion. Since you are planning on adding dwarf seahorses to this tank I would recommend a serious eradication program or cycling a new tank for the seahorses. They drive dwarf seahorse keepers nuts and will kill seahorse fry or very small seahorses. Most of the dwarf keepers I know use Panacur to keep them in check, however the residual effects of the med would preclude using any of that rock, etc. in a reef tank.

P.S. If you want to see some macro images of couple of different species of hydroids go the the photo gallery at seahorse dot org.