Ok i'm not at all an expert in the field nor have I ever done it (so for your sake I hope someone else who knows stuff will give you more info)
But from being curious and looking into it a little in the past I'll say that my impression is that cannabis is too hungry for it. The problem is you've either got fish living in what they consider dirty water, or you have the plants lacking in nutrients. The technique definitely works for some people and some plants, but I think that they would be low feeding types.
Just for a little more info though, another thing I picked up is that it takes a rather large fish tank in proportion to number of plants to get any system to run right.
But keep looking into it and hopefully an aquaponic gardener (of what ever species plant) will chime in too.