What is this Clear Sac?

kdragon64 · Dec 25, 2017

Merry Christmas everyone.

Can anyone please help me ID this thing that showed up in my tank this Christmas morning? Not sure if it's a nice gift or a Trojan horse.

It's clear and has some white spots within it, it sways in the flow like it's some type of gel. Just showed up this morning on one of my rocks. Only attached at the bottom.

mamedina · Dec 25, 2017

If you have bubble algae could be a popped vesicle

Lazys Coral House · Dec 25, 2017

It looks like a mucus bubble from a wrasse or other fish that creates them. They do it when they sleep so predators can’t smell them

Lovemyreef2015 · Dec 25, 2017

Looks to be a sleeping cocoon, mucus produced by the fish sleeping. Any wrasses in the tank?

kdragon64 · Dec 25, 2017

Thanks so much for the quick responses, however, I have never had any bubble algae in the tank and the only wrasse that I have is the blue line cleaner wrasse that I've had for about 8 months and never made this before, it's smaller than the fish, and the fish doesn't seem to ever stay still long enough to use this thing. I was thinking it could be some type of egg sac? I really don't know though. The only fish that have a possible mate is the clownfish, but this doesn't appear like the pics of their eggs. Otherwise, I have a bunch of snails that I thought maybe created it, but I have no idea which snails it may be.

Lazys Coral House · Dec 25, 2017

It is from the cleaner wrasse. It makes a new one every night.

Zack K · Dec 25, 2017

Agreed. wrasses makes a new sac every time they fall asleep. Most of the time it is just blown away before you can spot it.

4FordFamily · Dec 25, 2017

Cleaner wrasse is your likely culprit.

kdragon64 · Dec 26, 2017

Ok, thank you all. Sounds like a strong consensus. I learn something new in this hobby practically every day.

NormanB · Mar 31, 2020

I know this is an old thread, but I have the same thing and no wrasses in the tank.

TracyLynn · Mar 31, 2020

I have found this randomly in my tank as well, I have a Blue line cleaner wrasse. Apparently Parrot fish make this sleeping cocoon as well.
Older article about it here:

Fish build mucus cocoons to fend off parasites

Just as some people must sleep with mosquito nets to ward off the bloodsuckers, coral reef fish apparently spin cocoons of mucus before slumbering to keep away biting parasites, scientists find.

www.nbcnews.com