I just ordered a sunsun HW404B which is supposedly an upgrade to the 303B. Now it seems like pretty decent sized canister (for a 55 gallon that is) so how much media do I need? It comes with basic media, 4 filter pads and 1 plastic mesh layer. I have 4 liters of matrix and 5 bags of seeded Hagen biomax for aquaclear filters. Any suggestions on what else to cram in it? Also what should I use for a prefilter layer before the filter pads?