@krj-118- So still no metal.
Yeah - I would still say no metal in a shark tank - At all. At very least make sure no metal can have direct contact with the water in any way.
While sharks maybe be fine with metal(in the form of ship wrecks) in the open ocean. In tanks it can be quite a different story - since tanks are a very tiny faction of the size of ocean.
Even the largest Public Aquariums in the World are only equaled to about 1/1000th(at best) of the size of just 1 square mile of Ocean. And the largest private shark tanks are likely in the range of 1/10,000-1/20,000th(at best) of 1 square mile of Ocean. So any potential problems are greatly magnified and concentrated.