ID pls: video of hydroids or ?jellyfish?

[SteveConn]

Took a video through my microscope to get a better look at these. Found about 20 of them pulsing near the top of the water in a rubbermaid "tank" I am curing rock in. Just curious.. They are about 1-2mm in diameter with a browinish color.

http://www.youtube.com/watch?v=tjlUvRIgWrU&feature=plcp&context=C3a53ba6UDOEgsToPDskLvaVsAOgbr19fOctU7ZK2x

[Nano]

thats a very cool video! thumbs up. They do look like some type of hydroid/jelly fish to me, and if I'm not mistaken aren't uncommon in newer set ups and tend to die off, but hopefully some one who knows for sure can confirm or dismiss what I have said.. still though that is a really cool look at them!

[ScubaSteve]

99% sure it's a jellyfish ephyra. Haven't the foggiest as to what species though. The other 1% is a coral planula but most planula are ciliated rater than having a medusa form.