How does Blue Tang fish protect itself?

Answer 1

It has sharp spines that will extend out and can slash up predators. They can also stick or cut your hand as well.

When scared or feels threatened it will also "play dead". It will lay on it's side usually in a hole or under a rock.

Answer 2

If your fish is lying on it's side, it probably needs more oxygen in the tank than you're providing. Tangs and surgeonfishes are very oxygen sensitive and need the water to be nearly saturated with dissolved oxygen. They also need a lot of vegetation in their diets and some extra vitamin C rich foods. They're also prone to saltwater ich (Cryptocaryon), saltwater velvet, bacterial infections, and head and lateral line erosion.

Their primary means of protection is the sharp spine near the tail. This is very sharp "like a surgeon's scalpel", which is why they get the name surgeonfish. It's NOT venomous, but can deliver a deep cut, which can become infected.

Answer 3

All tangs have sharp poison spikes (usually white) on their tails. The fish will rarely use these unless they feel threatened. These spikes will protrude and deliver (in most cases) a poisonous sting usually into the mouth of the threatening fish. It will swing its tail back and forth.

I have never heard of them playing dead to survive.