MarkL;599487 wrote: Rubble an idea years ago but no one does it any more. 2nd chamber is good to have a intake media rack. They have a web site. most people use filter floss on the first rack,chemipure and purigen on the other 2 racks. remove false floor from the first chamber to fit a longer heater.The reason people quit using rubble is the same reason people dont use bioballs they trap unwanted waste and food.In a tank under 20 gallons water changes are your friend dont waiste the money on a skimmer. Ive had most nano skimmers they do ok but when i removed them the tank still did the same.The ato is your best friend for a nano.