A blue tang fish has extremely sharp spines on each side of its tail and on its back. When it is threated or alarmed, it will thrash its tail from side to side and inflict damage to the predator. This characteristic keeps it safe from predation.  

It also has very sharp teeth. This allows the fish to feed on algae from rocks and coral.

In times of fear, a blue tang fish is capable of turning see-through, which allows it to mix in with its environment. This allows it to be practically invisible until the predator(s) passes.