The style is upflow. The pump discharges to the bottom of the cylinder and water flows upward. The idea is the media doesn't become compacted. Tank water enters the reactor in the red tube, exits in the blue. Clear line is for CO2, the bubble counter in the center, excess gas that may buildup is recovered through the fitting in the the center of the top flange and cycled back in.
To supply water, I tapped a 1/4" John Guest into the line after my main pump for my sump return. Flow (drip rate) is controlled by a valve between the tap point and the reactor. Had originally put the valve after the reactor but found I was getting weeping from the flange since I was pressurizing the unit. The weeping was probably more from the irregularities in depth of the groove I cut for the o-ring while trying to get fancy but since replaced the flanges with no grooves, but left the valve on the input.
Remember the reactor is to maintain Ca levels, not raise then. To get the values initially up, bought Ca and Mg from
littlesilvermax . Something I've started to look into to maintain the Mg levels is adding
ZeoMag, mixed with Ca reactor media at 10%.