Shark - what type?
Show tank - how big?
Shark = big mouth with big teeth = large infrequent feedings of meaty food = spikes in ammonia = need for rapidly adapting high capacity biofilter. Rapidly adapting high capacity = rapid procuction of nitrate.
I think, personally, the "difficulty" is in the need for a LARGE tank..... subsequently that large tank has problems assocaited with it....namely water management on a large scale.