Why are my ceriths doing this?

[eschaton]

A few weeks back, I got a bunch of ceriths from reefcleaners. Mostly mini-ceriths, because I've heard they reproduce well in tanks.

Their behavior in the tank though has been...odd.

Basically the ceriths will not leave the glass. All they do is stay on the glass (mostly the side wall) and eat diatoms off. They don't seem to go onto the sand bed or the rocks at all. They form clusters (as in the picture), and often climb out of the water entirely for long periods as if they're nerites or something. I don't know if this damages them in any way but after a day or so out of the water I knock them back in.

Has anyone experienced similar behavior?

 

[Mattt]

Mine did this for a while when my tank was only a few months old. Now they all hang out in the sand bed until lights out.

 

[Mike N]

Mine all congregate on top of my mag cleaner and then disperse/graze when the lights go out.

 

[SaltyCupcake]

I wanted to chime in and say that mine do this as well in my tank. I used to help them back down onto the sand bed with my brine shrimp net, but they really seem to dig it up on the glass for now so I stopped bothering them in case moving them was stressing them out.