Im 95% sure this will work just want to make sure my plan is a good plan. I have just ordered a Hydor 350 for my 55g. I am currently running a HOB Aqueon 75. I run my own filter pads in the current filter. My plan is to dedicate the first media tray to my used/seeded media, then have the other two trays for the ceramic and new sponge. This will work right? I have a sponge filter in the tank too, its not doing much but its take the edge off. So yeah? I don't really want to run both filters for a couple weeks, I don't think its necessary. EDIT- I got the 350, not the 250.