I don't have the media rack on my tank
This is what I did in my tank:
Filled the media rack with bags containing Matrix (Seacherm), the big size rocks. Matrix increase the biological filtration by increasing the surface ratio of rock (this is a kind of artificial rock). Its porosity is high so you increase the population of Anaerobic bacterias that will use your Nitrates.
For phosphates I was able to add a 20G fuge filled with macro algae. On top of that I hanged a HOB acrilic fuge on the 20G side and filled it with Matrix.
After 2 months I am having now the issue of 0 Nitrates and 0 Phosphate. That is not good. So I have returned to daily feeding and will add a couple of fish in the fuge.
Bottom line, this give you an idea of biological filtration to solve your problem. At list you can fill with Matrix the media rack provided with the RSM. For cleaning you take the bags every 6 months and shake it in NSW during a WC. Nothing else, you do not want to kill the bacterias.
Cheers
Daniel