carto tanks go around the carto and feed juice to the carto via a hole in the side of the carto usually put there buy you using a carto punch, dremel tool, or saddle valve. You can also buy cartos made for tanks with the holes in it. The easiest tank system is the vivinovas. Thet are essentially a atty with wick that go into the juice tank and soak the juice up to the coil. The atomizer heads are replaceable or rebuildable. I used cartos for a long time, first by themselves, then in tanks and now all I use for my allday setup is vivinovas. Its just easier.