Not a full blown cliché but it's one of those things you almost only see in PEPLUM films and wonder how practical it would have been to have such a thing.
Raf Baldassarre is thrown into a tank filled with acid in HERCULES & THE CAPTIVE WOMEN. In the following shot we see a skeleton in the liquid.
In THE SON OF SPARTACUS, a rebel is tossed into a tank filled with deadly fishes (Moray?) which results in the following scene captured below.