There’s a moment in a hobbyist’s journey that separates them from a breeder. It is the day that your peaceful community tank erupts with hundreds of little dots swimming about. If you’re like many novices, you are surprised by the wild display, which more closely resembles chaos than excitement. The line between being proud and panicked is thin. Preparation is often the deciding factor.
Livebearing species such as mollies produce young that are not eggs but are instead born fully formed (i.e., fry). While this makes some aspects of the process easier, other aspects becomes more complex. Since there are no eggs to scatter in a corner and forget, you have to deal with live fry instead. The offspring is self-sufficient immediately, and the parents are predators that view the offspring as food. When you understand the process in advance, what was unexpected becomes a plan.
How to Breed Molly Fish
Twelve popular varieties (from simple Black Molly to fancy-pants Harlequin) are broken down in the visual guide. They all have their own temperaments and genetic traits. For starters, anyone who keeps mollies should go with solid color types; those is hardy and cover up minor water imperfections better than metallic ones such as Silver or Gold Dust. But going for appearance only isn’t an option.
You need to match the adult size of the fish you’ve chosen with the size of your tank. Sailfins are much bigger then their short-finned cousins and demand more strict water care as well as room for vertical swimming. Avoid overcrowding troubles later by getting the species right first, then consider breeding.
First practical obstacle is recognizing sex, in fact, both sexes are different. Females have a triangular fin shaped more like a fan, whereas males has their anal fin modified to what is commonly called a gonopodium, i.e., a sort of spear-like pointy fin. Why does it matter? Mollies are polygamous, so there will be a lot of chasing if you have as many males as females in a tank. Chasing is stressful for both sexes and results in either injury or stunted growth.
To avoid this, I recommend sticking to a 1:3 male/female ratio (infographic). You won’t need more than two males, and it will reduce harassment. Let nature take its course, but don’t turn your aquarium into a stress zone.
After pair bonding, physical indications of pregnancy appear. As the brood grows within the female, you’ll see the gravid spot just ahead of her tail darken considerably. Her belly starts to “box out,” meaning it becomes square edged instead of retaining its rounded curve. While this is always a good indication, behavioral cues are far more certain. A pregnant molly tends to isolate herself around the perimeter. She will often stay within heavy cover (e.g., Java moss) or near the substrate. She might also stop eating altogether. Both are instinctive measures to prepare for delivery and not necessarily symptoms of disease.
The chart below outlines those eight critical clues so you can determine whether your Molly is pregnant or suffering from something else. One mistake many make is confusing labor with laziness. This causes them to miss the mark by either over-tending or letting go at the absolute wrong moment. Black mollies will only take about three weeks, whereas something like the much larger Yucatan Molly may be carrying their babies up to eight weeks.
So, the gestation period must stay stable. Any drastic fluctuations in pH levels or even cooling temperatures could force the mom to either prematurely deliver the fry (which are now weaklings) or absorb them into her body again. To avoid this, keep the heat constant at somewhere around 78-80 degrees fahrenheit. Keeping the mom’s metabolism elevated makes sure everything goes according to plan and the fry develops properly. You should of kept it stable.
Once they emerge, it is a time of fast swimming and vulnerable babies. Moving your mom ahead of time or having her in a breeding trap will protect the newborns but only for about half an hour before the parent fish go after the fry. Because regular flakes are too big and sink too quickly for those tiny mouths, the first few days require microscopic food sources like infusoria or newly hatched brine shrimp. Getting the feed right in the first 48 hours makes more difference than anything else for whether the fry live. As they age, you can move them up to crushed flake and eventually spirulina wafers.
Dedicated breeders face another challenge with color genetics. This involves pairing a male and female of the same color (e.g., pure black) to get pure offspring, while knowing that recessive genes in their lineage may show up again later on. Achieving trait stability takes time (selective breeding across multiple cycles) and keeping records. But as long as it’s sustainable, the casual hobbyist can enjoy the genetic diversity that nature gives us, there’s no need for perfectionism here.
You’ve got the right balance of instinct/nutrition/environment when a brood of fry grow up to be happy and healthy adults in your tank. Seeing that little molly swimming proudly with his/her parents is the true reward for your labor. Actually, it should of been easier than this. All the furnitures you buy helps too.
