Ok thanks guys. I'm really thinking about biological filtration. My XP3 already has those mech. filter pads so I think I'm good there. I do have two bags fool of poly-fill but I don't really want to use it since I want bio. filtration. I was think the pot scrubbers so I guess thats what I'll go for. I'm thinking about cutting them up in squares and just throwing them in there so hopefully water could pass through and around them better. Thanks guys!