cucumber

[cag]

I have a really nice pink cucumber. It has the little spikes etc. My concern is that it seems to be shrinking. It stays up on the glass all the time, and doesn't go down to the sand to feed. It practically inverts itself when I feed bio plankton in order to filter feed. But that doesn't seem to be enough. Any ideas on how to get it to feed in the sand, or how else to make it happy?