90 Gal reef and 50 gal predator tank builds

[Oxymoron]

The skimmer that I have decided to go with is the following
http://www.superskimmer.com/SumpBuddy40.htm
This skimmer has been selected based solely on its footprint dimensions.
I am hoping that It will make do on my tank. I did have my heart set on a bubble king. However after trying for quite some time to make it fit under my cabinet I eventually found this one. I actually have only found about 3 skimmers that would fit in the small footprint I have available and this ones seems to be the best bang for my available size.
The ATO will be custom built and the calcium reactor will be a whole new challange.
Does anyone know of a suitable ca reactor for a 90 gal + 30 gal sump with an extremely small footprint? Or perhaps a custom builder?