heres a tip for getting a higher chance for pink tails. find and fight the pink flan things.
i think they have 20,000HP. when there are only two left count the amount of damage youve done to one and when your certain the next attack will be the finisher do the attack and before the person youve selected attacks use a pheonix down on the enemy. the pink flan should be defeated then revived by the pheonix down. do this repeatedly to increase the chance of receiving a pink tail. this trick works for other rare items.