You can always benefit from bio media in any tank. Especially at the beginning stages.
I would either do one of two things after the tank is established and you are using matrix.
Either take the matrix out completely after tank is mature with lr in it
Or keep it in the filter and take it out once a month with your water change and give it a good shake in the dirty tank water you've pulled out. This stuff can trap a lot of particles. Just like blowing off your rock work before a wc
Sony Xperia Z3