You can actually set up some controllers to work in series so there is no way they both come on at the same time. I think you can do this with the love controllers (http://www.coleparmer.com/catalog/produ ... 000&pfx=EW)
If I remember right you have a johnson, what you could do is use the love for chilling then use the johnson for heating. I don't think the heating is as "important" as the chilling
