It is an adaptation that they have developed to defeat other siamese fighting fish for mates and/or territory.

They can't because , Siamese fighting fish are very territorial & will fight . Obviously they're named fighting fish for a reason (: . Your welcome ...

deffo salt watercoz i have a tank full of siamese fighting fish and i keep them in saltwater

Myron Gordon has written:

'Siamese fighting fish' -- subject(s): Siamese fighting fish

Yes. The Betta splendens (scientific name) known also by its common names Siamese Fighting-Fish and the Siamese Fighter.