I think i found a "jellyfish" in my DT. HELP PLEASE!!

[Trigger 180]

ok, I found something that looks just like a jellyfish. it moves like a jelly fish. It's about 2-3mm across at the bell. are these "hydroids"? is it bad? should I worry? where did it come from? I did a little research, and some people are literally talking about "torching" their rock, like seriously taking it out of the tank and putting a fire to it (crazy). I looked around my fuge, and found these tiny little aptasia looking things (see pics). I am a little freaked out about this, but hope that I am just over reacting. can anybody ID this critter? and more importantly, do I need to do anything about them? if so, then what? thank you o gurus of aquatic wisdom! please see attached:

 

[Calappidae]

They look like hydroids. They'll die off on their own they're really difficult to keep alive if you wanted them.

 

[Trigger 180]

well, we did not "acquire" them on purpose. we are not even sure how they got into the DT to begin with, but here they are! lol! but seriously, they are a creature that I\we have never encountered. Being that they look like jellyfish, and we know that jellyfish are know for stinging the %^&*@ out of prey items, my first impulse was to research. after looking up hydroids, I am more than a little confused. some people say they will just die out. others have said that they will kill corals and fish. others have said that they are worse than aptasia. I am trying to figure out what we got, and what is the safest thing to do for our reef. if they are harmless, I have no problems leaving them be. but if they are not, we are not sure what should\can be done... anybody got experience? ideas? comments?

 

[Betta132]

If you keep them alive, then you may be able to keep certain species of nudibranch that only eat those.
They probably won't survive... Just keep an eye on them. If they spread radically, you have a problem. If not, you're fine.

 

[Calappidae]

well, we did not "acquire" them on purpose. we are not even sure how they got into the DT to begin with, but here they are! lol! but seriously, they are a creature that I\we have never encountered. Being that they look like jellyfish, and we know that jellyfish are know for stinging the %^&*@ out of prey items, my first impulse was to research. after looking up hydroids, I am more than a little confused. some people say they will just die out. others have said that they will kill corals and fish. others have said that they are worse than aptasia. I am trying to figure out what we got, and what is the safest thing to do for our reef. if they are harmless, I have no problems leaving them be. but if they are not, we are not sure what should\can be done... anybody got experience? ideas? comments?

They'll annoy corals and are a threat to very weak fish (actually I think just seahorses..) but they do die off. The "Jellyfish" are actually a part of a hydroid's lifecycle before it anchors on rock.. The life cycle for jellyfish actually is the same but in the opposite direction where it detaches from a rock.

Whether they're jellyfish or hydroids, during their free floating stage any filter or powerhead will tear them to shreads.

If you wanted to somehow keep them alive you'd have to actually target feed them, keep your water qualiy so perfect.. and I think some lighting.. They're more difficult to keep then to kill.

They're bad hitchhikers.. but out of all the bad ones are the easiest to deal with.

Speaking of hitchhiker they came off your live rock.

I believe the nudibranch betta is refering to would be berghia correct? I'm not too familiar with berghia killing hydroids just anemones (aiptasia specifically which looks almost exactly like a colonel hydroid minus the whole free floating life cycle and such)

 

[Trigger 180]

well it's good to hear that they are not too hard to get rid of. also, interesting to note that hydroids have an "opposite" life cycle to their cousins (jellyfish). we are not trying to keep them, just wanted to know if they would harm the residents of my DT. if they become a nuisance, then i'll post some more. until then, thanks for all the help you guys! also, if you have any ideas or comments, feel free to add, I love the education!