If the plastic is in any way porous, it'd work along the same lines as real LR
, but not nearly as effective since most live rock is soooo full of inner passages and holes etc.
And FYI, I buy live rock all the time for the aesthetics, not just for the filtration aspects.
I have many tanks now (more and more as time goes by!) and I love getting new rock and watching it in the QT tanks... all the mysterious life on the stuff (especially when ordered straight from the ocean packed in water!) is so cool and fascinating.
My 2 cents.. sorry for the threadjack.