Is this a jellyfish??

[TexasReefer82]

Saw this guy swimming in my sump refugium this morning. No idea where it came from.

 

[vetteguy53081]

Can’t open video on my phone but may be a hydro jellyfish which is a hydroid.
Net and discard

 

[DeniseAndy]

It is so cute though!!!! Probably best to remove it.

 

[dedragon]

I would remove it as well from the DT but that is really cool, maybe diy a kriesel for it either in a second tank or the sump if you have room

 

[Gargoyle]

Saw this guy swimming in my sump refugium this morning. No idea where it came from.

That's not the same as what usually gets ID as hydroid jellyfish on this forum. Unless it's just a more mature stage. Don't act too quickly to throw it out. It may be an interesting wet pet that doesn't harm the rest of your tank.
But I like interesting things in my tank.

 

[Unitylover]

Its kinda cute, maybe you could put it in a seperate tank lol

 

[dedragon]

Nope, i had to find that as well. It appears that hydoids do have a free swimming stage as well so probably just one of them, not the biggest cause of concern though pest wise

 

[EricR]

It sure looks cool!

*I had moon jellyfish for 1.5 years but they're much more relaxed (slower) and wouldn't have done well in "flow" normally used in reef tanks,,, plus obviously look different.

Don't know enough about hydroids to comment on that but, if it's a jellyfish, looks to me like it's working hard so my uneducated guess is that it'll burn through its low body mass pretty quickly expending that much energy.