one day my molly had a big hole in her side and i dont know what happened she died yesterday.i just want to know what happened so i can prevent it in the future.
Can you describe what the "hole" looked like exactly plus give more information on your tank and its stocking etc, we can't really help you much on the info you've currently given us.
well the hole was kind of egg shaped. and she was in with guppys ,other mollies,platys,swordtails,bleeding heart tetras,some sort of line tetra,and a pleco.