Aggressive Mollies

[smiles669]

Hey everyone!
So my girlfriend has had an aquarium set up for almost a year now and she is starting to have problems with it. it is a 20 gallon tank, and i have her setup with enough filtration for a 70 gallon tank. Her temperature is perfect, and the tank has been fully cycled for a long time. from the start she had mollies, swordtails, and guppies, and as this was her first tank, she did run into a few snags and lost a couple fish, but then things worked out. Then came the ick issue, but i made sure that was solved aswell. She now has 2 mollies, 3 swordtails, and 1 guppy, and a small bristlenose. the problem we keep having, is every time she adds something to the tank, it doesnt last longer than a week! I only let her add one fish at a time and it never makes a difference. Shes lost a dwarf gourami, lost a few rams, another gourami, and 3 dwarf crayfish! the only thing i can think of is her mollies are harrassing everything to the point that they become too stressed and die. she always says she sees her mollies picking on everything she adds to the tank. can anyone help with this? does anyone have any ideas of what else the problem could be?

 

[rpgmomma8404]

The two mollies I got as a kid were pretty bad. One of them killed the other molly and bullied the other fish. My mom took him/her back the next day. I don't have any experience with them other then that. From my understanding though and what I have been learning on here. They do better in brackish tanks.  

 

[Lunar Jetman]

What about trying to quarantine the mollies for a couple of weeks after new fish go in. This will give the new fish time to settle in and mean the mollies are effectively put back into a "new" tank and they'll have to find their position in it. You could also move some decoration/plants around to break up territories/areas and that may help too.
 
How big are these mollies though? And what are the water stats, ammonia, nitrate, nitrite?

 

[smiles669]

The mollies are probably a couple inches long. The water stats i cant get. shes in school and a couple hours away from me. Thanks for the help guys, i think shes going to look into finding a new home for the mollies.