how to differentiate between malabar snakehead and giant snakehead?

[ground]

both channa micropeltes and channa diplogramma look almost similiar. i have a juvenile channa, which was unnamed at the shop i had purchased it from, although i was certain it was a micropeltes when i had bought it.
how do i tell if it is a malabar or giant?

 

[stackdeck]

It should be the giant if not labelled otherwise.