One way is to excrete it out with the rest of the waste products, such as ammonia, across epithelia or gill (see Weihrauch et al. 2004). But then this would be processed through several organ systems and tissues which could potentially be harmed by the metals along the way. Another way is to hide it away somewhere where it can be relative inert and slough off a large portion all at once. Sort of like bulk trash pickup day when the undergrads leave for the summer.