Hi everyone,

Yesterday I bought a new female dalmation molly to balance out the ratio male to female mollies in my 20 gallon tank.

The problem is my male sailfin molly has been pretty aggressive towards it, and I don't know how to make it stop.

I would appreciate advice, do I need to separate him from the rest of the tank in my backup 10 gallon?

Tank info:
Temp 78 F
All levels are good
I have 2 female platies, one female swordtail, one white skirted tetra, a fruit red eye tetra, a female balloon molly, a male sailfin molly, and a new female dalmation molly.

Give it a day or two. If he keeps it up, then it might be best to separate them. Also consider the hiding places you have; are there enough plants for everyone to hide in?

If she starts to show signs of illness or injury, then take her or him out of there. I got a platy two months ago that was so aggressive, we had to take her back to the store. She would pick at the others nonstop, to the point that they would roll over on their backs and even hide from her all day. If your male is like this, then he might be too aggressive for your tank.

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Creatures great and small, I love 'em all! But mainly the fish.

I've had this male for a few months now, do you think it would be possible to sell him to a different store than where I got him?

Many livebearer males continualy harass females and try to mate. One solution is to have lots of females, another is to put the males and females in different tanks.

A lot of LFS do take fish in for store credit; you might try calling around and asking. Places like PetsMart and PetCo don't do that, but a lot of local stores do. You could also try getting one more female molly, like NeonShark suggested, or putting the male into a different tank if you don't want to add any more or get rid of him.

For selling him, though, you could also try Craigslist to find interested buyers in your area. There's also a sell/buy/trade forum on this site, so maybe there's an Aquarium Forum member in your area who might be willing to trade. Whatever you decide, good luck with it!

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Creatures great and small, I love 'em all! But mainly the fish.