I have platys and neon-swordTails and zebra danios in my tank currently. I can see the male fishes are all fighting among themselves.
Platys: 2 male, 3 females -> 2 males fight with each other and visible injuries in scales.
Swordtails: had 3 male, 4 females -> 2 males dead, now with 1 male, the swordtails became peaceful.
Zebra danio : 2 (not sure if they are male or female) - bigger one was chasing all every other fishes whoever comes on its way. as a result, a female platy and the other danio has damaged fins.
The only worrying factor in my tank right now is fish aggression. Any help to solve this?
(not sure if this info helps: ammonia 0, nitrite 0, nitrate 10ppm. low light, low tech, lots of plants.)