how do you sex theses fish i have two both look the same in markings but one is large than the other with a big belly active swimmer and the other is a little smaller slimmer and hides in its cave the fatter one seems to bully the smaller one bitting at its head then snuggling up to it they were both the same size when i bought them the slimmer one wont leave the cave the larger one flares its gills and grabs the other by the head and trys to pull him out but at the same time the larger one seems to rub its self on the cave and on the smaller ones head hope this helps help welcome cheers john