I am new to this concept so I am not too sure how to build one , do I take a reg carto punch a holor two in the bottom of it and then slide it into a tank? is it that simple? or do I have to buy something other than carto's to go into the tank? If the former is the case do I fill the carto before I place it into the tank? I have to fill the tank before it is seated all the way down? I have been reading the tank forum and this is what I have figured out so far, please let me know your thoughts on this.