To keep the true nature of the trick a secret, Robert only hires blind stagehands and allows no one else backstage, and gets a new water tank for every performance. He has his blind employees cart out his floating dead Robert clones and store them in a warehouse, for reasons that are never adequately explained.
Perhaps because the greatest sin against nature is hiding your sin against nature.
OK, so when Robert books the theater for his Transported Man trick, he specifies that he'll be doing five performances a week for a total of 100 performances. That's 100 tanks over the course of 20 weeks. Where the hell is he getting all of them? There's no way to invoice that many tanks of that size and be subtle about it. And anyone who checks that order and reads a review of his magic show will immediately notice that not a single tank is being used onstage.
And it isn't like Robert is doing the trick once or twice before folding his tent like a gypsy to move to another town. He is performing his show five times a week in the same city for five damned months. He's parading his dark secret around in the open for anyone with half of a brain not poisoned by mercury from a yet-unregulated fishing industry to figure out. That's like hiding treasure in a box labeled "THIS IS NOT WHERE THE TREASURE IS." Moreover, Tesla, the guy who built the machine for him, knows full well how the device actually works and is bound to hear about Robert's famous trick sooner or later. How long do you think it will take Tesla, one of the most famous geniuses in history, to deduce what Robert is up to?