A Swarm of Something Living Under Hermit Crab's Shell

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Apr 14, 2013
I noticed my clown fish behaving strangely. They were swimming in very short, fast bursts so I went to the tank and noticed tiny, white tadpole looking things swimming around in the water and the clown fish eating them. I looked down and saw a hermit crab on a rock seemingly having difficulties keeping its shell on. The shell kept pulling away from the crab and every time it did, I saw a small red mass of something swarming underneath and the little white tadpole things releasing into the water. Does anybody have any idea what is going on? I will try to post a video I got of it. For some reason it is not uploading to Youtube with my phone right now.

ETA: After some research, I think I may have a female hermit crab who has reproduced. The picture of the red under the shell as well as these things swimming as soon as they hit the water seems to fit the cycle

Last edited:

Rob in Puyallup

Well-known member
May 5, 2013
Puyallup, Washington
I've had hermit crablets twice over since April. The first time in my QT tank, the second in the nano reef tank.

The larva lasted several days in the QT tank that had no predators, several hours in the reef tank with a Yellow Watchman Goby and a pair of Neon gobies.

The crablets reminded me of cartoon characters from Sponge Bob Square Pants.

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