hi , i have two triangle cichild in a 60 gallon tank. i bought them 1 year ago and they were the size of coin. now they are 15cm long.i have noticed lately that they dont look the same . one of the is darker(black) and the other is pale .since a few days the pale one stays near the decoration(an old sunk ship)and take the gravels in his mouth and spit it in the surroundings. it like he is digging or making a home . while the other one(dark) he swim around the tank . i have 4 blue acara too in that tank and the pale one pick on them when they come close to the home . i would like to know which one is the male or female? help me please .thank you