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Mollies are a beautiful type of aquarium fish that come in different body shapes, colors, and fin configuration. They are easy- to-moderately-hard to care for, and do not die easily.
However, mollies are a little delicate when chilled or exposed to environmental stress. Plus the fish are particularly prone to an ailment known as shimmies which is more a symptom of stress than an actual disease.
Overall, all molly types are peaceful, with males only slightly aggressive when establishing a pecking order.
Therefore, you can maintain them in a community aquarium with other peaceful and medium to large species that prefer hard water and can tolerate elevated salt levels.
To keep your molly fish happy and healthy, add them in a planted fish tank with the water temperature anywhere from (6.5 to 7.5).
Moreover, make sure your aquarium water is hard (about 10 to 20 dGH) with elevated salt level, and you may also want to add a teaspoon of salt per gallon of water for the fish’s optimum health.
Mollies require a tank size anywhere from 20-gallons to 30 gallons, and because they are omnivores, feed them both meaty foods and plant matter, particularly algae-based foods.
That said, let us now delve deeper into the molly fish tank to learn more about the fish types, care, and breeding and how to provide suitable conditions for the fish in your home aquarium.
Molly Fish Overview
The most common scientific name of molly fish is Poecilia latipinna and are usually found in Mexico, Florida, Texas, California, North Carolina and up to Virginia.
However, in case you come across mollie in your local fish store, they will most likely be placed in either of three categories, sailfin mollies, short-finned mollies, and lyretail mollies, hence the scientific names Poecilia sphenops, and Poecilia velifera are also common in the aquarium fish trade.
Even so, all mollies are livebearers and are closely related to guppies with both species being part of the Poecilia genus. The fish have an unusually high resistance for saltwater (akin to guppies and platies) and are unbelievably prolific.
Male mollies grow up to 3 inches long depending on the species and females about 4 inches in length which they reach about 6 months of age. Adult black mollies can grow up to 5 inches in length.
However, the fins get their ultimate beauty and attain average size only during the second year of the fish’s life.
The average lifespan of most mollies is anywhere from 2 to 4 years, but with proper care, they can live up to 5 years.
Types of Molly Fish (Including the Black, Ballon and Dalmatian Mollies)
There are many varieties of molly fish because of extensive breeding in the aquarium fish trade. However, there are only a few major ways to distinguish a molly based on three major differences: Coloration, Fin configuration, and body shape.
Molly Fish Colors
Molly fish come in a variety of colors, but all are derived from the 3 primitive color schemes: White, orange, and black. Out of this, you will get about 4 or 5 popular molly types with the others less common.
The most common color variations in mollies include:
Black Sailfin Molly
Also called giant sailfin, Mexican sailfin and simply sailfin molly, this type belongs to the family Poecilia latipinna and are pure black color and grow to an average size of 1.5 to 2.5.
Sometimes, you may get another popular closely related type called the black lyretail molly that has the same black base color, but with white highlights on the fins and lyre-shaped caudal fin.
Gold Dust Molly
This molly type belongs to the Poecilia sphenops family and is a perfect option for people who love beautiful color variations from the drab black molly.
Gold dust mollies are usually black or gold and sometimes with the front half mostly yellow to gold and the rare half black.
This species is also called gold panda molly, and like others in the family, they can to adapt to a variety of salt levels in the aquarium.
The platinum molly also called the Mexican lyretail molly, giant lyretail or Yucatan molly is a color variation of the Poecilia velifera (a third and name molly species) characterized by a platinum gold coloration.
The fish species is peaceful and prefer hard water.
The dalmatian is another unique color variation of the Poecilia latipinna, the sailfin molly. It has a black and white body like the classic dalmatian and is sometimes called marbled molly or marbled sailfin molly.
The fish can adapt to a variety of salt level in the fish tank.
Other common color variation include:
- Gold doubloon molly
- Harlequin Sailfin molly
- Marble lyretail molly
- Blood red molly
- Green sailfin molly
Molly Fish Types (According to fin configuration)
Usually, molly fish come in three major tail configuration which includes the sailfin, short-finned mollies and lyretails.
The Sailfin Molly Fish
The sailfin mollies which are from North Carolina to Texas and the Yucatan peninsula of Mexico have a broad caudal fin that is large, rounded and sometimes tipped with black.
The fish body is essentially ‘oblong’ with a small and dorsally flattened head.
Wild forms are generally light grey, although breeding males may be greenish-blue. Even so, there are a couple types that exist which include the black sailfin molly.
The scientific name of sailfin molly is Poecilia latipinna.
The short-finned molly also called common molly is native to freshwater streams and coastal brackish and marine waters of Mexico.
Wild forms are a silvery color and can produce fertile breeds with many Poecilia species including the sailfin molly.
The wild fish types are dull, but there are a lot of selectively bred forms that include the black molly, white molly, golden molly, balloon molly, lyretail and dalmatian.
The scientific name for this species is Poecilia sphenops.
The lyretail molly, commonly called the Yucatan molly is a less common species but still quite popular in the aquarium fish trade.
It is outwardly similar to the sailfin molly, though larger overall and with a higher dorsal fin especially in males.
In the wild, they are considerably big, reaching up to 4 inches in male, and almost twice that size in females. However, captive-bred types grow only to the size of sailfins.
That said, the dorsal fin is the most distinctive characteristic with nearly 20 fin rays from where the fins meet the back, and males spread the fin to display s distinct fan or trapezoid shape. Hence the name lyretail molly.
Molly Fish Types (According to Body Shape)
Almost all mollies will have the same body shape albeit having distinct colors and different dorsal fin configurations.
However, there is the selectively bred balloon molly that displays a more arched back and a large, rounded belly.
Even so, balloon mollies still come in a variety of colors and fin shapes. The fish may have a large lyre-shaped caudal fin and either the short or sailfin shape.
Balloon mollies are however mostly a breed variation of Poecillia latipinna with the most common color being black, yellow, and white. They are probably the only molly type that is distinguishable by its unique body shape.
That said, read more about the 10 popular molly fish types you are most likely to find in your local fish store.
Are Molly Fish Easy to Care for?
Mollies are not hard to take care of, because they are adaptable to a wide range of conditions and water salinity, though particularly happy in hard water.
In the wild, they inhabit freshwater streams in the Americas, with a few reports of the fish being found at sea. For this reason, they can be maintained in both freshwater and saltwater aquariums.
Molly Fish Tank and Water Conditions
Keeping mollies in an aquarium will depend on whether you have sailfin or short-finned breeds. Usually, the short-finned types can be maintained in a smaller tank, sometimes even in a 10-gallon setup.
However, the recommended tank size for short-finned mollies is from 20-gallons, while for sailfins, you’ll need 30 gallons or more. This is because Poecilia latipinna species develop a larger and broader caudal fin.
Another reason you would want a bigger tank is since they are easier to maintain in terms of water quality, especially since some mollies are hearty feeders, which then means a bigger bioload.
The best water conditions for mollies include hard water that is about 10 to 30 dGH and a ph, preferably 7 to 8. Some mollies fish types can tolerate acidic water better than others.
Moreover, maintain your water temperature within the 68°F to 80°F range to keep your mollies comfortable and in top health.
Add a couple of plants in your tank since mollies prefer heavily planted environments, but remember to leave enough swimming spaces for your fish.
Floating plants are especially useful to create hiding spaces. And if you intend to breed your mollies, the plants will provide shelter for baby molly fish.
However, some mollies have an appetite for live plants if not properly fed, so only go with species that can handle rough fish. Good options include Java fern, Sagittaria, Vallisneria, and Anubias.
Of all livebearers, mollies are arguably the most sensitive to water quality, so they require a heavily filtered aquarium, but they still are largely adaptable.
The situation is exacerbated by the fish hearty-appetite which means more water quality issue to the otherwise largely tidy fish species.
The best type of filters to use in your mollies aquarium are hang-on-back or canister filters depending on the size of your fish tank.
Canister filters are better when keeping large mollies or if you have a large community aquarium. While hang-on-back filters are perfect for small 10 to 25 gallons tanks.
Moreso, change your water weekly making sure the parameters remain stable as it is less stressful for the fish.
You can also do 25 to 30 percent water changes every 2 weeks to a month in a lightly stocked fish tank, though this is more likely to affect water stability compared to 10 percent water changes.
That said, there is an ongoing debate as to whether mollies can live in brackish, or better still, saltwater tank. And whereas there is no one fit all answer, some molly fish have been proven to be quite tolerant of this condition.
Ergo, consider your fish independently to determine where they can (or can’t) survive.
Molly Fish Food—Diet and Feeding
Mollies are omnivores that feed on insects, green growth, and plant matter in the wild.
Consequently, in the aquarium, they are not picky eaters and will eat most fish food you offer them, but make sure the diet is made up of adequate amounts of both plant matter and meaty food and especially algae.
Algae-based flake foods make a good base diet, with occasional treats of freeze-dried bloodworms, tubifex or brine shrimp, plus a herbivorous diet.
If you don’t have ample time to feed your mollies blanched vegetables, offer them Spirulina-based pellets in their diet.
Feed your molly fish several times a day because of their hearty appetites, and remember to offer them enough food rest they feed on your live aquarium plants.
However, give them food they will eat in 3 to 5 minutes, then remove leftovers (especially food they don’t seem to like) to maintain safe water chemistry.
What Kind of Fish Can Live with Mollies? (Tank Mates)
Mollies are peaceful and make good community fish, hence can be maintained with a host of aquarium species.They are especially fine when kept with equally peaceful and large species.
Even so, their tank mates need to be capable of surviving in hard water with elevated salt levels.
Other mollies make good companions for the species you have, and so will others closely related fish like guppies, platys, swordtails, and Endler’s livebearers.
Overall, all livebearers get along with molly fish since they have same aggression levels and breed in the same manner.
Other good companions are bottom feeders because they won’t bother mollies that rarely occupy the bottom half of an aquarium.
Betta fish and gouramis get along fairly well with mollies, but mainly keep them with female betta, even though there are calm males.
You could also try keeping your fish with angelfish, although angels get quite aggressive as they grow larger in size, so you may need to separate them later.
When keeping mollies with either angelfish, betta or gouramis, remember to follow best stocking practices to avoid maxing out your fish tank.
Here is a list of good companions you should consider maintaining with molly fish.
- Betta (females)
- Angelfish (with caution)
- Cory catfish(but don’t add extra salt rest the cories will be harmed)
- Loaches(like with cories, avoid adding salts in the tank)
Molly Fish Breeding
For the most part, mollies are easy to breed. They are liveberers, so instead of laying eggs, they give birth to live, free-swimming baby mollies.
Usually, a single female produces up to one hundred babies (even more).
Since mollies display hierarchical tendencies, the male with the biggest fins and boldest colors will most likely mate with multiple females.
For this reason, the ideal combination of male and females is one male for multiple ladies.
When copulating, you will notice the male fish under the females, and if the mating is successful, you should have baby mollies in about 3 to 5 weeks.
That said, mollies get to breeding age quite early in life with females able to reproduce at about 6 months of age, so don’t be surprised if you get babies from fairly young fish. However, males become sexually mature at around 12 months.
Pregnancy clues in molly fish vary from one type to the other, but most don’t display noticeably strong and bold sings or changes. Hence, the easiest way to identify pregnant fish is by their enlarged abdomens, and the female will start searching for shelter or dark places to hide.
They mostly hide under plants in the aquarium which can provide enough shelter both for them and the babies.
Pregnant Molly Fish Care
A pregnant molly should be accommodated in a birthing tank away from other fish, or at least consider using an aquarium net breeder to protect the mother and baby fish.
Moreover, if you choose to breed your mollies in your fish tank without moving the mother, you’ll want to plant the tank heavily such that babies have places to hide, especially because molly fish infamously cannibalize their youngs.
Either way, moving the babies and mother does stress them out to the point of risking harm to the baby fish.
So, should you opt to move your pregnant female, don’t wait too close to the birth date as stressed mollies have more aborted and stillbirths.
Also, pregnant mollies feel more relaxed in warmer water than normal tank temperatures.
Caring for Baby Mollies
Once you female molly fish has given birth, you may want to reintroduce her into the main aquarium to keep her from eating the young ones.
Feed your baby mollies ground-fish food of the same type that you offer to your adult mollies. Flake food should form the base diet and supplement with a variety of denser meals.
Worms like daphnia, blackworms, and blood worms work well, and so does brine shrimp (live or frozen). Also, feed them algae-based foods.
Wait for your fry to double in size (in about 2 months) before reintroducing them into the main aquarium. At this time, you should also be able to tell male and females apart.
Another way to determine when to introduce your baby mollies to the main tank is if there are too big to fit into other fish’s mouths.
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Have fun with your lady betta.
…have fun keeping molly fish.