Ah, now I don't know what you mean by pellets? Our thoughts were rowaphos and maybe carbon?
Hahaha don't panic! There are bio pellets/ pearls - which that reactor is designed for. They reduce nitrates.
Rowaphos (or similar. There are loads of brands.) simply absorbs phosphate for export. It's best used in a reactor but you only need the media to 'simmer' at the bottom. Too much flow and it will grind to dust and into your display. I presume that reactor would work for rowa so long as you can keep the flow lowish.
Carbon can be ran in a reactor as well but general opinion is it is better simply in a media bag in the sump as again it can grind to dust if fluidised. Plus if doesn't require the water to pass it quickly to be effective.
Hope that helps!