Betta smaragdina are closely related to splendens. Meaning they have aggressive traits as well. The problem with buying smaragdina, maichai, and imbellis are that they are also bred for fighting...just like splendens.
No you don't need brackish water, they all come from the same swamps just in different parts of Thailand.
Who am I? Well I am a Junior Member of the International Betta Congress and a breeder of white HMPKs, red dragon HMPKs, black/red dragon HMPKs, metallic multi HMPKs, blue masked HMPKs, and now multi color HMs. Soon to add black HMs. I will be showing in New Breeder class in fall of 2012.