Is It Essential To Have Minimum 6 Tetras In A Shoal?

[pochacco_18]

I have a mini shoal of black neon tetras (3) and mini shoal of black skirt tetras (3)

Is this okay?

 

[Lateral Line]

With the information given, the simple answer is, no.

 

[Parin]

A shoal is dozens or hundreds of fish.
A minimum of 10, the typical "aquarium shoal", is already a mini-shoal.

So I must agree with Lateral Line, the answer is no.