Media for Frag Tank

Hi guys new to this forum,I've just set up a frag tank and want to keep it fairly simple,low maintenance etc,I've got a hob filter and don't really want to use any reactors or skimmers as I intend on doing regular water changes,also there will be no fish in it,maybe the odd snail and also will bare bottom for easy cleaning,just wondered what you guys think would be a good media for the hob. I was thinking something that can be put in a bag ?? Thanks.