How long does it take for a red eared slider's shell to harden?

A red-eared slider's shell begins to harden shortly after hatching, but the process can take several months to a couple of years to fully complete. Factors such as diet, environment, and overall health can influence the speed of shell hardening. Young sliders typically have softer shells, which gradually become more calcified as they grow. Providing proper calcium and UVB lighting can support healthy shell development.