I can accommodate different currents as there are 4 powerheads I can adjust to many different directions. I also use canister filters.
I've heard they like slower moving waters. I was more interested if a 22" knife-fish had different or specific needs than a 12" one - besides room. I am building about a 3 1/2 foot long, by about 10" tall and 10" wide open on both ends cave. The bottom will be the aquarium bottom ... filtered rocks and gravel.
Hopefully this will look like a really nice cichlids rock pile when done - except the knifefish living inside. I have all sorts of great rock.