There is probably ~6000gph total. 5 cuft of K1 in moving bed, 5 cuft of Bio balls in Shower, ~3.5cuft of Lava rock in Shower should be able to handle a great load, aerated MB and Shower media is many times more effective than traditional submerged media filtration. This often makes this type of filter very cost effective, since you can have much less media for a given load.