Question About Cherry Red Shrimp

[sadguppy]

We have had four red cherry shrimp in our tank for a month or so, at the start they used to hang out on the plants together (having a shrimposium, if you will). Then they disappeared and we thought they were dead - we never saw more than one at a time but usually couldn't find any at all.

Now, after a two week disappearing act, they're all back.

What were they doing that meant that they all disappeared at the same time? I know they moult but surely not all together??

 

[sadguppy]

Now one seems to have lost its colour but is very active. Any ideas?

 

[Bungy]

They probably went into your filter. Seems to be most likely outcome.
I breed shrimp and have thousands of cherries but only use sponge filters now, some other tanks with fish I have a canister filter and they always end up in there, quite happy to released back into the tank every 6 weeks or so after a clean...!