Do you have small gravel in your tank? What kind of tilapia, blue, nile, mozambique? Blues and nile mature young. Blue = 2-3 months. Nile = 3-5 months. Mozambique (Black Tilapia) = 5-7 months.
I asked about the gravel because in my tank the dominant male builds a nest and becomes VERY aggresive. The fish don't pair up. the males gather harems. The females when becoming gravid will give big, open-mouthed "kisses" to any fish coming near it, except her chosen male. I just lost a 7" male that a female 6" female tore the tail and lower scales off of because he would not take no for an answer. In the picture, there is no mistaking the nest. The Dom. male is in the lowere left with mush-mouth (she looks like she was stepped on. no left eye and deformed lower jaw) beside him. The Fake plant mat is there so the male cannot see the other fish from his nest and prevents numerous attacks. The other females on the top came over for the pic thinking they were gouing to be fed.
