I have a 29 gallon tank that houses seven neon tetras, two female koi swordtails, two female red velvet swordtails, and three snails. I opted for an all female group to try to avoid breeding and aggression, although one momma did drop fry shortly after bringing her home, as to be expected I guess! I've had the kois in there for weeks without any problems and recently introduced the red velvets six days ago. Everyone was getting along great.. Until tonight. One of my red velvet girls is harassing the other. She doesn't bother the kois at all, she seems to have her eyes set on the other red velvet in the tank. I double and triple checked the gender of them because I initially suspected I may have gotten a sneaker male, but they are very much both female. But she keeps chasing the other red velvet around the tank and nipping at her and following her into all of her hiding spots. The tank is heavily planted with plenty of hiding areas, but she seeks the other red velvet out! I also caught her nipping at my (enormous) mystery snail but she grew bored with that quickly. This seems to happen in intervals. Sometimes she is absolutely fine around the other RV, but it's like she gets bored or something and starts harassing her for hours on end. I can tell it's stressing the other RV out. Could this be because she is pregnant and about to drop fry and I just can't tell? She shows no sign whatsoever of pregnancy, her stomach doesn't square off and there is no gravid spot that I saw clear as day on my previous momma. I can't even see a slight difference in coloring at all! Has anyone else had any experience with hostile females in their tanks? Should I remove her? Water chemistry is solid and good at 0 ammonia, 0 nitrites and 10ppm nitrates.