Umbrella Thing

[Anonymous]

No pic yet, I'm hoping it won't be needed.

I noticed one in my tank 6 months ago, then it was gone. Today I've seen another.

About 1 mm across, picture an umbrella, open, stuck in the rock by the sharp tip end. The umbrella part just keeps opening and closing - quickly, maybe 1 beat every 2 seconds, irregularly. So it's like a tiny jelly fish swimming nowhere and stuck to the rock by a projection coming out of the top.

Any thoughts?

 

[Anonymous]

Probably the polyp stage of a jellyfish or hydroid. If you'd like to find out more google "strobilation" or "medusa stage" or both.

 

[Anonymous]

Thanks Matt. If that's what it is, I guess it would have to be a hydroid.