Is It Safe To Introduce A Mollie To An Existing Group?


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Hi. I have a 10 g tank that currently contains 3 female balloon mollies (and a small gold spot pleco that will be rehomed once he gets a bit bigger.) I've had the mollies for 5~6 weeks now.

My test strips don't measure ammonia, but the fish don't show any signs of ammonia poisoning. Nitrites almost none, nitrates low and within the normal range. I do 50% water changes every week with a gravel cleaner.

I thought of introducing a new female, or a new male, or maybe a female and a male. I was wondering if it's good for them to make the fish school larger? Is it better for them to have a male in the tank or are the girlies better off without a male?

As for the hierarchy, I haven't noticed anything very pronounced. One of them used to chase the others around the tank, but that was in the first 1-2 weeks after I got them. I put her in timeout in a hatchery net for about an hour, and after that she called down and stopped harrasing the others. Now, none of them harrass each other and they seem pretty friendly. They don't harrass the pleco and he doesn't harrass them, they don't interact much except they try his food occasionally when he's eating.

If I add a new female, is it possible the 3 mollies I have will not like her or not let her into the group? Or is it relatively safe to do that?


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Rhode Island USA
2 years
I would invest in an API test kit before getting more fish so you are able to measure Ammonia Nitrites and Nitrates more accurately ( test strips aren't very reliable and don't test ammonia as you know). Also 3 ballon mollys in a 10 gallon is a fairly full tank seeing they have a large bio load. I would up the tank to a 20 or 29 then i think it would be safe to add a male and female then you can use your 10 as a grow out tank when they start breeding like crazy. Good luck!!
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