Molly fish are a versatile and popular choice for freshwater aquariums. Gain all the knowledge you need to take care of them healthy and happy right here!
Contents
Molly Fish – Quick Facts
In a rush? Check out the quick facts about Molly Fish below.
Fish Info
| Scientific Name | Poecilia sphenops |
| Common Names | Molly, mollies, short-finned molly, common molly |
| Family | Poeciliidae |
| Appearance | Dull, silvery color; light gray in color; greenish-blue color; dotted with spots |
| Difficulty | Molly fish are hardy and easy to care for fish. |
| Distribution | Molly fish inhabit freshwater streams and coastal brackish and marine waters from Mexico to Colombia. |
| Lifespan | The lifespan of a molly fish is approximately five years. |
| Shoaling | Yes |
| Temperament | The temperament of molly fish is peaceful and easy-going. |
| Keep in Groups of | A group of four or more mollies should be kept together. |
| Tank Mates | Guppies, Swordtails, Platies, Neon Tetras, Danios, Corydoras, Bristlenose Pleco, Dwarf Gourami, Angelfish, Southern Platyfish, Oscar, Suckermouth Catfish, Green Swordtail, Gourami, Cichlid |
| Diet | Molly fish eat algae, live or frozen bloodworms, daphnia, and brine shrimp. |
| Length | The length of molly fish is about 3 to 5 inches. |
| Sexual Dimorphism | Males are more torpedo-shaped and have bigger fins than females. The males also have pointed anal fins, while females have rounder anal fins. |
| Breeding Difficulty | Breeding molly fish is easy. |
Water/Tank Recommendations
| Water Type | Freshwater fish, but can be adapted to brackish/saltwater |
| Water Temperature | The ideal water temperature for Molly fish is between 72 and 78 degrees Fahrenheit. |
| Water pH | The ideal water pH for molly fish is 7.5 to 8.5. |
| Water Hardness | The ideal water hardness for molly fish is 15-30 dGH. |
| Tank size | The minimum tank size for molly fish is 10 gallons. The recommended tank size is 20+ gallons. |
Introduction
Molly fish are a very popular freshwater fish that have been kept in aquariums around the world for many years. With their simple yet stunning looks, they’re one of our favorite species to recommend!
Not only are these fish easy to care for, but they’re also fun to observe. They are a great choice for aquarists of any experience level.
In this article, we’ll go over all there is to know about molly fish and how best to keep them happy and healthy. You’ll learn their lifespan, tank size requirements, diet recommendations, breeding tips, and more!
About Molly Fish
The molly fish is a type of live-bearing freshwater fish that comes from the genus Poecilia. There are many different types of this species, and they all have very similar care requirements.
There’s one main difference between each variety: coloration. They come in a variety of colors, including greenish-blue or silvery-white, and there are also slight differences here and there on their bodies!
These fish also love to breed!
Appearance
Molly fish come in a variety of colors, including:
- silvery in color
- light gray in color
- greenish-blue color
- dotted with spots
They have short and stout bodies (3 to 5 inches long).
The dorsal fin is triangular shaped and rear pointing. The tail is forked or fan-shaped. The anal fin tapers slightly toward the end of it, while the caudal fin is rounded at its tip.
Mollies have a pointed lower jaw that protrudes slightly from the rest of their head. They also have small black eyes surrounded by white sclera.
Their Length
The average length of molly fish is 3 to 5 inches. Still, there have been times when they surpass this range by up to an inch in large tanks.
In captivity, mollies can reach maturity in as little as four months.
Lifespan
The Molly Fish is considered short-lived fish, with a lifespan of only five years.
If you want to make your molly fish last as long as possible, providing them with the best care possible and keeping them in optimal conditions are musts. Poor water quality or suboptimal pH levels can shorten their lifespan significantly.
Aside from keeping track of the water conditions, you’ll want to make sure that your fish are kept in a large enough tank. In small aquariums, many fish can suffer from stress and illness.
NOTE: In addition to keeping your molly fish in a large enough tank, you’ll need to perform regular water changes. This will help keep ammonia and nitrates at bay. Ammonia can cause stress on the fish and make their lifespan significantly shorter.
Sexual Dimorphism
One of the main ways of determining the sex of this species is by observing the size and shape of their anal fin.
Males have pointed anal fins, while females have rounder anal fins. The males also have bigger fins.
Males are usually larger and more torpedo-shaped, while females have a smaller build.
Habitat
Molly fish originate from northeastern Mexico and the lower half of South America. They inhabit streams, lakes, lagoons, ponds, and even brackish water near shorelines.
These tropical freshwater fish prefer shallow warm waters with plenty of plant cover for shelter and safety. Each group of wild mollies can have up to a dozen males trying to court one female!
Their favorite plants are duckweed or floating plants, such as water lettuce.
Caring for Molly Fish
These colorful freshwater fish are hardy and easy to care for. With a fairly low level of difficulty when it comes to their tank requirements, this makes them great for beginners.
In fact, molly fish have become very popular among beginner aquarists looking for an affordable yet rewarding species to keep (this is why you might see so many of them at local aquarium shops).
As far as water parameters go, the short-finned molly doesn’t need much by way of special conditions. They do fine in a typical tropical tank. However, there are some general tips regarding keeping these types of fish happy that you should follow.
Diet
Molly fish are omnivores. They are willing to eat anything you give them!
The easiest way to feed these fish is through commercial dry foods. Standard flakes or pellets work fine. Make sure the food has all of the nutrients they need and that it’s nutritionally balanced for their requirements.
You can give them live foods to eat, like bloodworms, brine shrimp, and other high-protein snacks (if you want to mix things up). In addition to protein, mollies really enjoy some algae in their diet as well. You can use dried algae wafers if your fish prefer them.
How Often & How Much to Feed Them
Give your mollies food either once or twice every day. Young fish may need to be fed 3 times per day, though.
They should finish their food within a couple of minutes. If it takes them too much longer than that, then you may be giving them too much to eat.
NOTE: If you notice your molly fish being fussy, quarreling with other species in the tank, or acting lethargic, it could be a sign of disease.
Possible Diseases
Mollies are prone to suffering from common freshwater fish diseases, such as Ich. The disease is usually caused by stress or poor water conditions and can be fatal if left untreated. If any white spots show up on your molly, it’s important to separate them from the other fish in their tank before treating them with copper-based medications or salt baths.
Tank Setup
Setting up the tank for molly fish is easy. These freshwater fish are quite adaptable and can tolerate a wide range of conditions.
The most important thing when setting up their habitat is to create an environment that suits their needs as a schooling species. As we mentioned earlier, they need space to roam (with plenty of hiding places) in order to feel comfortable. This means getting a large enough tank with plenty of decor where they can swim together if desired will be your highest priority.
Another feature you might want to consider adding is plants or natural substrates like pebbles or gravel. Molly fish love having some cover in their tank.
Aquarium Size
Mollies must have at least 10-gallon tanks. A larger tank size of 20+ gallons would be optimal.
NOTE: These are schooling fish, so it’s important to make sure that the aquarium has enough room for them to swim and school together comfortably. If you keep a small group of four or five in a cramped space, they will likely develop behavioral issues.
A larger tank size will also help you to house more fish together. This is important when considering the potential for breeding.
Mollies are hardy and can adapt to life in a wide range of water conditions, so when it comes to this, you have a bit of leeway in setting up their tank. However, if you want your fish to thrive and live the longest possible lifespan (which we do), follow these recommendations closely.
Water Conditions
As with any freshwater species, keeping high-quality and consistent tank conditions is key to the health and happiness of your Molly fish
PH
The pH level of the water should be around 7.5 to 8.5,
Water tests should be performed weekly, at least, with a pH meter or test strips being used as necessary to ensure that your tank is safe for its inhabitants.
If the pH levels in a tank become too high (above 8.5) or low (below 7.5), it could result in medical issues for your fish and negatively impact their ability to process oxygen efficiently. This will be fatal if left unchecked, so regular water monitoring is essential.
Temperature
Molly fish thrive in water temperatures ranging from 72 to 78 degrees Fahrenheit. The recommended tank temperature should be about 75 degrees.
Keep the tank water temperature in check and keep an eye on the gauge to avoid sudden shifts that could harm your fish.
NOTE: Mollies are also quite hardy when it comes to temperatures outside of their preferred range. This means you have a bit more flexibility as an aquarist, which can be very useful in the long run.
Hardness
The hardness level of the water in your fish tank is a very important aspect to consider. The ideal range for molly fish is 15-30 dGH.
If you want to be absolutely certain about getting this number right, pick up a testing kit. It won’t be long before you know exactly how hard or soft your water is.
Filtration
The best kind of filtration for molly fish is a hang-on-back canister or an internal filter.
Molly fish are actually very good at keeping the tank clean, but they can’t get rid of ammonia. This is where your filter comes into play!
NOTE: A strong filter will also help keep nitrates in check. Nitrate levels that are too high could harm or even kill Molly fish.
Aquarium Plants
Plants are a great addition to any freshwater aquarium. However, you want to ensure that the plants are compatible with molly fish before adding them to your tank.
Mollies love having plants around because they provide security and comfort. The poeciliids use plants as cover when feeling scared or threatened. You may also witness them playing in the leaves frequently too!
Some good options for your molly tank include Java moss, hornwort, Amazon swords, and Anachris, among many others. Just remember that there’s a fine line between having enough room for swimming AND enough plant coverage for hiding/comfort.
Behavior and Compatibility
Molly fish are active and fun-loving fish that get along with a wide range of tank mates. They normally spend their time swimming throughout the tank, using plants for hiding spots when needed.
These fish can be shy at first, but once they feel comfortable in their environment, they become more outgoing and playful. This is especially true when kept in large groups (more on this below).
They can often be seen swimming together in a shoaling or schooling pattern. This is their natural way of staying safe and feeling comfortable in the aquarium.
Molly fish are peaceful and non-aggressive, which means you don’t have to worry about them starting trouble with other tank mates (assuming your pick compatible species). In fact, these fish prefer being kept in groups rather than alone.
How Many to Keep Together
The best number of molly fish to keep together is four or more. This will allow them space to swim, as well as providing a potential breeding group if they choose to do so.
Do not exceed six in one tank unless you have an aquarium that’s 20 or more gallons. In this case, you could house 12 females with six males for a “breeding colony” habitat.
Temperament
Molly fish are peaceful and easy-going. They get along fine with other like-minded fish species and can be kept with others of the same kind without any problems whatsoever (no fighting or territorialism).
Molly fish are very active and will spend most of their time swimming around the tank. They’re quite curious creatures, which means you might see them checking out every corner of your freshwater aquarium!
Tank Mates
Molly fish make wonderful community tank mates for other peaceful fish. They do well with many types of non-aggressive freshwater species. Here are some molly fish tank mate ideas:
- Guppies – These small and colorful tropical fish work great as a complement to your molly aquarium. The guppies will spend most of their time in the upper half of the water column, which leaves plenty of room for your mollies to swim in peace.
- Swordtails – Swordtail fish have long flowing tails like that of a platy or Molly, but they’re longer than those found on other common freshwater species. This makes them more adept at swimming fast through the middle part of the water column where light is abundant, leaving quiet areas open for Mollies.
- Platies – Platyfish are an easy match due to similar habitat requirements and coloration patterns. Like Guppies, Platys will stay mostly in the upper halves of tanks without much disturbance.
- Neon Tetras– Also known as neons, these little guys can live in groups making them ideal mollie tank mates! Their bright colors allow them to stand out while staying out of each other’s way.
Here’s a list of some other potential tank mates for your Molly Fish:
- Danios
- Corydoras
- Bristlenose Pleco
- Dwarf Gourami
- Angelfish
- Southern Platyfish
- Oscar
- Suckermouth Catfish
- Green Swordtail
- Gourami
- Cichlid
Breeding
Breeding molly fish is very easy and can be done with minimal effort.
In fact, they are one of the fastest-breeding freshwater species around.
To initiate this process, simply raise the water temperature to 78 degrees Fahrenheit (or above).
It shouldn’t take long at all before you see little baby “fry” swimming around!
Are Molly Fish Fish a Good Choice For Your Tank?
Molly fish are a great choice for any freshwater tank. They require little attention, and they’re hardy enough to get along with other species.
We highly recommend getting some molly fish!
Pros
- Molly fish are definitely one of the most common freshwater aquarium species because they’re so easy to care for. They require minimal attention but will provide a lot of fun in return!
- They also have such an expansive genetic variation that you can choose your ideal color and pattern with ease. This makes them great starter fish for new aquarists who don’t want to spend time learning about the needs of rarer species.
- We also love that these fish are so active and playful. They’ll swim around the tank, exploring every inch of their habitat. This makes watching them a joy!
Cons
- The biggest issue that you’ll encounter with keeping molly fish is their breeding habits. These fish are livebearers and can produce a lot of fry at once, which can quickly overpopulate your tank if you aren’t careful about how many to keep together.
Conclusion
As you can see, molly fish is an excellent choice for pretty much any freshwater tank. The low-maintenance nature of this species makes them a great addition to your home aquarium!
Nina has been interested in fish and aquariums for over seven years. She started out as a keen amateur, keeping a few fish in her home aquarium. However, she quickly developed a passion for the hobby and began to learn more about different species of fish and how to care for them properly.
Over time, Nina’s interest turned into expertise, and she became known among her friends and family as the go-to person for all things related to fishkeeping. Her advice is sought after by both novice aquarists looking to get started with their first tank, as well as experienced hobbyists who want tips on improving their setups.
In addition to being an expert on all things aquatic, Nina also enjoys gardening and baking (especially making cakes!). She grows many different types of plants in her garden – both for aesthetics and function – including flowers, vegetables, herbs and shrubs.