Surprise, Surprise Surprise!

[Timfish]

I was doing maintenance on a system when this stuff showed up. It's a nice surprise to have something spawn or hatch out just would like to know what it is. They're pretty tiny, maybe 200 microns (1/5 mm) if I had to guess. With a magnifying lens they were really round, flattened on one end and had 2(?) short tentacles. They move pretty fast though, there's no current to speak of as the pumps had been off for awhile. I apologize for the video, wasn't exactly ready to film a spawning or hatching event.

 

[JumboShrimp]

Wow! It's like a swarm of bees!

 

[JGT]

Cool, what was in the tank?

 

[Timfish]

Cool, what was in the tank?

Lots, it's a 3 year old mixed reef. But I don't think this is from a coral spawn*. It would take several days for fertilized eggs to develop into larva or planula that would swim on their own and the filters would remove most most of them pretty quick. It's not fish larva, they're not able to swim very well at all and mostly just float. One thought, since these "bugs" are actively swimming and look like they're trying to stay together, is these are adults and this might be a spawning aggreagation.


* Although this system does appear to have had monti's successfully spawn.