Worried about my mollies!


New Member
Apr 23, 2019
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I have a 120L fish tank. Have about 30 fish. Currently have 5 mollies and 4 fry. The first breeding pair of mollies were added to the tank over a month ago, they got on fine and everything was good, we then added a Dalmatian female molly and again everything was ok. Then a couple weeks later we added another male molly he got on fine with the other male but didn’t seem to be interested in any other mollies just swan around by himself where as the others all swam together. The Dalmatian molly soon gave birth (pregnant when brought) and we have saved 4 fry which are in a floatation tank. A week or so later woke up to find the male molly of the breeding pair had died. We shortly after added another breeding pair of mollies which are fine but strangely the male molly won’t leave these ones alone and still pays no attention to the 2 first females...

Now noticing the 2 females acting strange, not swimming around a lot keep hiding and just don’t seem happy. Also one of them keeps her dorsal fin flat and she never brings it up. They both seem pretty sad and not sure what to do. They also spend a lot of time at the surface of them tank! Or under the floating tank near the fry. If not they are hiding


Fish Guru
Jan 26, 2008
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Perth, WA
Can you post some pictures of the fish and a short video of them?
Set the camera's resolution to its lowest setting so the images are small enough to fit on the website. Take some pictures and check them on your computer. Post a couple of clear images on here for us to look at.
Upload the video to YouTube and copy & paste the link here. We can view the video at YouTube.

How long has the tank been set up?
How often do you do water changes and how much water do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?

What sort of filter is on the tank?
How often do you clean the filter and how do you clean it?

What are the ammonia, nitrite and nitrate levels in the tank?

What is the GH (general hardness) and pH of your tank water and tap water. This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).

How long have you had the fish for?
Have you added anything new to the tank in the last 2 weeks?

Do a 75% water change and gravel clean the substrate each day for a week or until we work out what is going on.

The following link has information about what to do if your fish gets sick. It's long and boring but worth knowing.

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