I found a gorilla crab in mine that killed my dwarf hermits. Are you sure if you added the CUC so soon part of the cycle may have damaged and killed them.
I dunno… they seemed fine for several weeks. On the upside, they're cheap enough that I can bung some more in and see what happens.
I always feed extra for my CUC so they have food also. Minute food hits the water snails are out and seaserpant star.
What extra food specifically do you put in for them?