exactly the same problem swan, not sure if mines a plakat male but it has definitly shown aggresion to my other male, enough to kill him! When I introduced a new male betta the same problem occured(flaring gills and such) yet the 3 other females showed no aggresion. When I put the "female/male plakat" into a spare tank it started to make a bubble nest, is this not a male behaviour?
Just to add swan and I brought the females from the same lfs unbeknown to us that there was problems.
