So I found this fiber splice closure at work it was missing the guts. Looks like they planned on using it but didn't have all the pieces. So I acquired it. I thought it would make a great reactor. We also have a plexiglass covers for cement boxes that I used to make the lid. I tried two different designs both would work. Here are some pictures. The plan is to add a pipe all the way to the bottom then the water rise up through the media and back to the tank.