Topic: I’m thinking about getting some mollies to put in my fish aquarium. I have heard some stories that they can be somewhat aggressive. Is that true? A friend of mine told me they killed their guppy fish. Can they live with guppies or other tropical fish? How mean can molly fish be?

*Awarded Answer
Posted by Jesse E: Its awesome to see you doing your research on your pet fish. It’s pet keepers like yourself that make for better homes of these animals. Lets answer your question now.

Molly Fish Aggression Levels

Molly fish aren’t that aggressive for the most part. The only way I could see a molly killing other fish is if it had a really long time to bully that fish to high stress levels. The males can get pretty aggressive when they are wanting to breed with females and chase and fin nip. But if you don’t have any fish that have really long fins you should be fine.

 

He needs lady friends. At least two. They’re easy to tell the gender of.  Top pic is the male Molly. Note the fin on the bottom of the fish that pins back along the body. Bottom pic is the female. Note the triangular “boat rutter” fin along the bottom of the fish.

How long have you had the fish? More than likely, your females are/were still carrying sperm from when you purchased them and those are the fry you see. A female live bearer can carry sperm for many months after a single mating with a male. So, let’s say you buy a female guppy and a male molly and 3 months later the guppy has fry. Chances are, they are guppy fry from the sperm she had stored, and not “muppies”, with the molly being the father.

What we thought was a female Dalmatian Molly, turned out to be male. One of our female guppy died giving birth. One of our female Molly had  babies a day before. I assumed all the fry were mollies but now I can tell some are hybrids. Look exactly like a guppy but have spots 😊. Super cute. None of my pics are very good, I’ll try again.

Same concept as lions and tigers mating or horses and donkeys or horses and zebras. They can breed, but the offspring are typically infertile.

Was thinking the same… So awesome.. I have some swordtails and guppies together maybe ill get a mixed breed some day lol

Not likely. They’re both live bearing, but from different families.

Im hoping to expand my tank soon with lots more species… Kids want a bigger tank plus going to need a seperate tank since the pet store gave me 2 preggo guppies and a prego swoardtail lol

So far we have 4 guppies, a pair of swords, 2 black mollys no glue on sex with them and 2 yoyo loaches… I just found out the loaches need a bigger tank? Right now everyones in a 20 gal… Im looking into a 40 or 50gal

With gender, female live bearers have a fin by the butthole shaped like a triangle or a fan. Males have a tube shaped fin used as a….Well it’s a boy part. Lol. As for the loaches, I’ve never had any but when it comes to fish I’d say the bigger the better.

I think both mollys have the fan tail.. My mom was telling me that mollys get whats called ick very easily aswell which im hoping isnt the cause id hate to lose all my fish to it.. I mean i know any fish could get sick and take out an entire tank… Im trying to think of some amazing bright beautiful fish to add to the colony when we upgrade the tank.

A good way to keep ick away is adding some sea salt. Mollies love a little salt in the water too.

Good to know ill have to get some next time im at petstore.. Im kind of new to fish.. Had them as a kid but they never seemed to survive.. Expect gold fish i could keep those alive for years so i accept any and all advice!

Yep lol. I used to obsess over mollies, guppies, swordtails, and platties. Mollies always gave me trouble until I learned about them liking brackish water. There’s likely some helpful books at the library, too. Always good to read up!

I’ve been reading about them since I posted. There are many muppie breeders! I’m really hoping they are infertile but not going to count on it. I’m taking pics right now.

I tried zooming in but they are just too small and fast, only a month old. Took a video but again it’s hard to differentiate between the Molly fry and hybrids.

I’ve had two male muppies before but have never successfully gotten any again. They both looked very similar to the pics from Google above and were definitely sterile (tested it with virgin females for almost a year, got nothing in return!). However, more times than not, even in many of the cases recorded online, the fish aren’t actually muppies or hybrids (they would have a definitely different look as adults). Many people seem to forget how long the female llivebearers can store sperm (up to 6 months or so) so just because there is only a female of one species and males of the other won’t necessarily mean they crossed. In many cases the species simply aren’t closely enough related to produce offspring, like mollies or swordtails or, for another example, parrots and chickens. They could mate, sure, but nothing will come of it. That all said, I’d LOVE to see any babies when they grow up so we can see what they are!

The Molly fry are growing much bigger than the ones I think are muppies, that’s why I just noticed it. I always noticed the difference in the eyes though. These new Molly fry all have the big black eyes. I’m so excited to see them grow!