Hi,im new to this hobby and site but I found some good info on ato and tried it,it seems to be working well so I thought I'd share. This is not my idea BTW. I use a tunze ATO with an apex controller. I built a box with a dpdt switch and a 120v coil. I took the tunze power leads for the pump run it thru the dpdt switch and now I can feed two pumps, one for fresh and one for salt water, when ac power is applied to the coil it switches pumps. So I plug the coil into an outlet on the apex tell it to go on when cond is too low. Now I'm ato with salinity in check, very cool!