I have a 14 gallon Biocube also and was told that the stock lighting/pc's were not strong enough to support a clam. You can upgrade the lighting to MH's if you want to keep clams.
As for anemone's, I hear so many things. I hear that you must have metal halide's to keep them, and then I hear that you may be fine to keep a bubble tip anemone with the pc's, so I don't know. You can try. I have a bubble tip anemone in mine, and it's been in there for 2 months and so far, it's been doing great. If I see that it is starting to suffer from just the pc's, which it may, I will take it back to the LFS, but for now, it's doing fine. It seems to be happy where it is, has only moved once since being introduced into the tank, and has stayed in the same place since!