Do you have the larger size or smaller size of Matrix? If you have the smaller size it would be a lot of work to attach moss to it. I use small lava rocks for most of my moss tying applications, it's cheap and its easy to break up into any size piece you need. You can get a big bag of smallish (1-3 inches or so in diameter) for cheap at any home improvement or garden store for cheap. The matrix should work fine though, moss will be able to attach to it easily.