Tadpoles?

[a2theb]

Found these darting around the tank about an hour after lights out. Sorry for the horrible pics but these are some fast swimmers! One is about an inch and a half while the other is/was about an inch long. It got sucked up into the powerhead and got spit back out in two pieces but is still swimming around as if nothing happened! I'm only a week into my setup and surprised I only saw them now. Any help would be great! Thanks!

[ChrisPrusha]

Welcome aboard, a2theb!! w000000000000000000000000t!!!

They are inch to an inch and ahlf long, eh? Hmmmmm...

[Twitterbait]

are they only out at night? do you see any corals being eaten or tracks?

[reefingaddict]

Do you think they could be larval fish? Do they actually swim or crawl?
Interesting to find out though.

[JEEP9783]

i had somthing like this, i was told that it was an peanut worm, and that they were harmless, mine also only come out at night

[Twitterbait]

that sounds correct too. the body shape is right for them too.

[a2theb]

Yes it only comes out at night. I found one swimming around this morning and shortly after the lights came on it retreated for the rocks. I found the second one on top of my mag float and caught a better picture with my DSLR. Not so tadpole looking anymore. What was cool was that you would see a red line pulse from back to front on top (sort of like an EKG). This one eventually wriggled its way free back in to the tank on the sand bed but looks like it's dying. Hopefully this picture will help ID these things. Thanks for all the help!

[ChrisPrusha]

It looks like a bristleworm, a beneficial scavenger.

[YLChik]

i second the bristle worm

[a2theb]

Thanks! Didn't know bristleworms could swim so well. Most I've seen are very small and always scavenging rocks, never out in the open water.

[LeslieH]

It's a polychaete in the family Nereididae and the sexually mature stage known as an epitoke. In some polychaete species the body undergoes varying degrees of change at maturity (not unlike teenagers ;D ). At max, the eyes enlarge, the internal organs are re-absorbed, the parapodia (the paired "feet" along the body) enlarge & develop frilly ends, the shape of the setae (bristles) change, and most of the body becomes packed full of eggs or sperm. The epitokes then swim up in the water column at night looking for each other. The male shimmys in tight circles around the female as they both shed their gametes. In some species that's it - they die - but in others which aren't modified as radically the parents go back to the bottom & survive for another round of spawning.

The pulsing red line is blood moving down the body.

[dobejazz]

Thanks Leslie !!!!

[ChrisPrusha]

w0000t for Leslie!!