My new canister has been up and running for a few days with no issues. I was thinking about cracking it open and tossing in the purigen and ceramic bio from my HOB so I can remove that filter from the tank. The canister came with 4 pads for the bottom tray, some bio balls and ceramic media which I tossed in the other two trays. I also added two new bags of purigen. Even if I throw in my HOB ceramic and bag of purigen I will have tons of space. A LFS has the box of Marineland small bio balls for like $11. I haven't stopped by to see how many are in the box, but I figure they will help fill up some space with the other bio balls. Should I grab these and toss in, or just buy some more ceramic? Or should I add some filter floss or something?? I just want to fill the trays up a little more. Also, is it ok to leave in exhausted purigen?? Or does it need to be removed? I'm on the fence with adding it to the canister, or just tossing it. It's brown, but not super dark brown like I have read it gets when exhausted.