Help with id (looks like jellyfish)

[Mmiyamoto]

I was watching my aquarium today and in addition to some undesirable planarians I identified something that I initially thought was dirt, but after looking better and using a microscope I noticed that they were animals similar to jellyfish. one of them came off the glass and went swimming through the aquarium (just like swimming in a jellyfish) would anyone know what animal this is, if they were the larval phase of a coral or something?
they measure approximately 1 to 2 mm

thank you very much.

 

[jcbasile]

It looks like hydroids to me so look up aquarium hydroids and see if that matches. I have them when I get some higher nutrient periods but as far as I know they aren’t harmful

 

[KJ]

These are tiny hydromedusae also known as hydroid jellyfish , and generally not a problem.

 

[vetteguy53081]

remove them with an old credit card and net it and discard. They are capable of stinging coral and multiplying also