Alright. I'm getting closer to what I want. Thank you iano7000 and O2Surplus!
So I'm taking down to half of the tank at a time to that I can play with it with less components at a time. In the long run it will cost more having to double up on power supplies, controllers, ect. But I want to take this one small step at a time.
'Transformers': LM2596 step down transformer
Power source: Fleabay 24V 3A brick supply
I'm leaving the CAT4101 as black box for now until I can figure out the rest of the components.
I think I'd be shorting myself current if I run the Ardiuno in parallel... But I like the idea of using a inexpensive standard power brick if possible. And do the fans need anything to protect them from too much current?