I have done that a few times also epicfish.... Some of the moss grew well under water, some did not grow at all.... In the end I didnt keep any because they were ugly

lol just long thin strands that never branched much.
Back on topic... thanks Cavan... I figured that I wouldnt need much as far as nutrients go.... but I wanted to make sure there were some there for the taking. I suppose another way to go about it would to be no substrate of any kind and just about a half inch of water from a well balanced planted tank.... with misting there after to keep it moist as water evaporated.
Oh well I already set up my little tubs with a thin substrate.... i think it should work nicely though they arnt getting much light because they are jammed behind my larger rubbermaid bins that hold more light hungry emersed plants. I think they will still do just fine though.... I will update when some new growth starts to show up.