Run a reactor in between pump and DT?f

I would run GFO for sure, but probably carbon too (at least for about a year).

I have a new problem though. My sump's return section is too small to put in another pump. I know the reactor should have the cleanest water going through it, but my only other option would be to put the pump in the skimmer section and have the outlet in the return section.

I know that's not ideal but my other option is to put the GFO in a media bag and put it in the baffles.