I decided I needed an ato, and on the cheap in light of aqu ring a fluval m40 AIO nano
So I had a float switch laying around, bought a cheap battery air pump off amazon with my perk points, as well as some rigid air line. Made a holder for the float switch with some plastic I had laying around from one of the mounting brackets for my JBJ ato. The end result is freaking sweet, all in all a DIY ato for about 25 bucks.
Step one, open case of air pump, remove air pump from housing, cut positive wire coming from battery to the power switch
Step two, prep the float switch
Step three run wires through hole drilled in air pump case
Step four splice wires, solder in place, replace air pump in case
Step five (no pics *sad face*) place air lines into ato reservoir
Step six, set it all up and watch it work
The basic idea is that air pump creates positive pressure in the container, forcing water out through the rigid air line