With the type of corys that you have to sex the females will be noticably fatter and kind of stockier than the males. Males also have slighty longer dorsal fins and are more lean and stretched looking than females. I agree that cool water changes work well, my paleatus are kind of fussy and I usually have to do multiple cool water changes in a day to induce spawning 2/3 small ones. Ive also had success adding some ice cubes made with treated water again a couple times a day 5/6 cubes at a time. Good luck