Whoah. Slow down.
artc's dont mix with other fish. There are some exceptions to the rule that I can think of, but in any case you will learn by trial and error like I have.
First off, you need a large tank. I would say 200+ gallons to house the Artc for life, and a larger tank will be needed to mix other species.
Since the artc is a bottom dwelling catfish, make sure it is the ONLY bottom dweller in the tank. territory fights will end in death.
so, your choices are limited- a large, aggro mid water fish or an arro that can hold its own. Also search for top water fish. Maybe an archer fish? You could also try a school of 2-3 scombs
you should be able to find a fish to mix with it, as artc's are very adaptable to water conditions. question is, what wont they kill?