I was never really into the whole crypt collection fad I saw some years ago.
But over the past few years I have really enjoyed them. and have been slowly growing my collection. There are 2-3 species now I have rotten luck with and can not keep them going. They do well, grow, send out leaves and them seemingly for no reason......melt away. Try to come back and then give up the ghost.
My C. crispatula is soldier. Thought it was gone twice and it has come back now with a few leaves but slowly growing taller. It seems to needs good water movement as many crypts do.
C. wendtii is all but bulletproof. brown, green all forms have done so well for me. growing in sponges only, pots, substrate and emersed.
I am always hunting for new "easy" to keep species and varieties.