I just picked up 6 boxes of Marineland's ceramic rings labeled for use as biofiltration media. I haven't used these before and, to me, they seem less porous than biomax and others I've used. They seem closer to a prefilter ring than a porous bio ring. Is this a case of them being very porous, just so small that they don't look or feel rough? I spent about $50 on this stuff and have only opened 1 box. I am wondering if I should go ahead and use it or take the 5 boxes back and get some biomax (which is a little more expensive). Anyone like or dislike these things for any reason?