This is my first sight about the “real” combat between different species of Gastromyzon. (sorry about the pic quality)
At first the dominant of SK01 (red tail) have combat with the more or less same size SK03 (blue tail), after sometime the SK03 give up, here the pic, (sorry about the pic quality)
The SK03 pushed back by SK01 to the left side of tank, and finally SK03 surrender. Soon after the loser retreat, the SK01 dominant come close to the biggest and the dominant of SK03 which stay not so far from it, and soon they involve in fighting.
The dominant of SK03 is the fish upper, SK01 below, and the SK03 loser is more below.
Because its quite bigger size than SK01, the dominant of SK03 can pushed SK01 little by little, some time they looks stay at their own positions but obviously they push each other showed by the movement of their pectoral fins and wagging tail.
note: The SK03 is at the left, its blue caudal fin looks grennish because flash lighth.
This combat happened in quite long time. (several minutes)
This blur pic with trace of its pectoral fins can showed how SK3 pushed SK01
Eventhough the SK01 looks pushed back by SK03, at the end the SK03 surrender with turning his head to the side and “run” back,
meanwhile the SK01 outomatically chase it for sometime. And the combat end with SK01 as the winner.
Face of the winner and also the most dominant in tank:
so many fishes 
Resistance is futile. You will be assimilated.
