Looks like hydra, very interesting organisms. Capable of tissue regeneration and DNA repair. Also they eat prey twice their size, so not a favorite in tanks.
Hydras, not a big deal for medium organisms but smaller fish and shrimps can get damaged or killed. Very interesting organism tho ! Same family as jellyfish i think.
dlgrayson 
Hail hydra
Possibly hydra.
Looks like hydra, very interesting organisms. Capable of tissue regeneration and DNA repair. Also they eat prey twice their size, so not a favorite in tanks.
Hydra. They can kill shrimp.
Some species of fish can eat hydra as well as Asolene spixi snails
Hydras, not a big deal for medium organisms but smaller fish and shrimps can get damaged or killed. Very interesting organism tho ! Same family as jellyfish i think.