Fish Momma Spotlight: Mollies
- Heather
- Aug 12
- 3 min read
Meet the Molly!
Mollies are one of the most popular freshwater aquarium fish and they're often recommended to beginners. But there's a little more to keeping healthy mollies than simply bringing a few home and dropping them into a community tank.
Let's meet them!
What Exactly Is a Molly?
Mollies are livebearers, meaning they don't lay eggs like many aquarium fish do.
Instead, females give birth to tiny, fully formed baby fish.
And if you put males and females together?
You're probably going to get babies.
Lots of babies.
A female molly can even store sperm and produce multiple batches of fry after mating, so sometimes a newly purchased female can surprise you weeks later.
How Big Do Mollies Get?
Those little mollies at the fish store aren't necessarily finished growing.
Depending on the variety, most mollies grow to around 3–5 inches, and some can become surprisingly substantial fish.
They're also active swimmers, so don't underestimate the amount of room they'll appreciate.
For a group of mollies, I generally like to start around 20–30 gallons, with larger tanks giving you much more flexibility.
Mollies Like Harder Water
This is one of the most important things people overlook.
Mollies generally thrive in hard, alkaline, mineral-rich water.
That means they aren't necessarily the perfect choice for every community aquarium simply because they're labeled a "beginner fish."
Your water matters.
And here's another common misconception:
Mollies do NOT need aquarium salt simply because they're mollies.
They can tolerate brackish conditions extremely well, but healthy freshwater mollies can do beautifully in appropriately hard, mineral-rich freshwater.
How Many Should You Keep?
Mollies are social fish and I prefer keeping them in a group rather than keeping a single molly by itself.
But there's something else to consider:
The boys can be relentless.
Male mollies frequently pursue females, so if you're keeping both sexes, it's generally better to have several females for every male. This spreads out the male's attention instead of one poor female being chased around the aquarium all day.
Or you can keep a same-sex group and skip the maternity ward entirely!
What Do Mollies Eat?
Mollies are omnivores, but they appreciate a good amount of plant-based material in their diet.
A quality tropical food supplemented with foods containing spirulina or other vegetable matter works well.
You'll also see them grazing around the aquarium, picking at algae and biofilm.
That does NOT mean they're your new cleaning crew.
They're fish.
And fish need to be fed.
Can Mollies Live in a Planted Tank?
Absolutely!
In fact, I love mollies in planted aquariums.
Plants provide cover, enrichment and places for fry to hide. Mollies look fantastic swimming through plants, and you'll frequently see them investigating leaves and grazing throughout the tank.
If you don't want dozens of baby mollies surviving, though, a heavily planted aquarium may make population control a little more interesting.
Those babies are very good at hiding!
Are Mollies Peaceful?
Generally, yes.
Mollies can make excellent community fish when they're kept with compatible species that appreciate similar water conditions.
However, they're active and sometimes pushy fish. Males can harass females, and individual mollies can occasionally become bullies.
That's another reason adequate space and an appropriate group are important.
Are Mollies Good Beginner Fish?
Yes — with an asterisk.
They're hardy, beautiful and entertaining fish when their needs are met.
But I don't like the idea that any fish is simply "easy."
Before bringing mollies home, make sure your aquarium is cycled, your water parameters are appropriate, you have enough room for a group and you've thought about whether you want males, females...
...or approximately 4,732 baby mollies.
Because mollies have absolutely no respect for your stocking plan.
Colorful. Active. Curious. And possibly pregnant before you even leave the fish store.
That's the Molly.
— Fish Momma
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