So just how easy is it to add an Avast Marine recirculating media reactor retrofit kit to your media reactor? Pretty simple by the looks of this video. We covered the conversion kit last year and if you have a media reactor and aren’t happy with the way it is performing — especially if you are using biopellets — then this $40 solution might be just perfect for you. Why convert your standard single-pass media reactor to a recirculating design? You get more ability to independently controlling media turnover and flow through rate for increased contact time.