Best resevoir for the Tunze ATO system and how far can you hide it?

[Hustler]

So im getting ready to hook up my new ATO and im still at odds with what to use for the RO water.... And how far away from my sump i can put this res....
Either a camping water jug, a 5 Gal pail or maybe a cube aquarium?
If it has to be close to my sump it will be out in plain sight so that sucks either way.... I was hopeing to hide it in the next room 5 feet away then i guess it wouldnt matter so much and i could use something bigger... Im adding about 3.5 gallons a day so i would like to get one bigger than 10 gallons.
Any ideas or solutions you guys can think of?