Mollies, also known as Poecilia sphenops, are a popular and hardy species of freshwater fish that are often kept in home aquariums. They are known for their unique appearance, which includes a deep body shape and a distinctive dorsal fin. They come in a variety of colors and patterns, making them a visually striking addition to any aquarium.
Mollies are livebearers, meaning they give birth to live young rather than laying eggs. This makes them an interesting species to breed and observe in the home aquarium. They are also known for being relatively easy to care for, making them a great choice for both experienced and novice fish keepers.
In this comprehensive guide, we will cover all aspects of keeping mollies in the home aquarium. We will discuss their appearance, lifespan, size, tank size requirements, water parameters, diet, and what to put in their tank. We will also cover common diseases, behavior, and temperament, as well as tips for breeding them in captivity. Additionally, we will delve into the history and origin of the species and provide answers to frequently asked questions.
By the end of this guide, you will have a complete understanding of the molly fish and be well equipped to provide the best possible care for them in your own home aquarium.
| Parameters | Ideal Range |
|---|---|
| pH | 7.0-8.0 |
| Temperature | 72-78°F |
| Water Hardness | 5-20 dGH |
| Tank Size | 20 gallons minimum |
| Tankmates | Peaceful community fish |
| Diet | Omnivorous, flakes, pellets, live and frozen food |
| Breeding | Livebearer, separate breeding tank advisable |
| Lifespan | 3-5 years |
Appearance
The molly fish is a striking freshwater fish that is well-known for its wide range of color morphs and hardy nature. They have a laterally compressed, elongated body shape with a deep, slightly arched back. Their dorsal fin is elongated and pointed and their caudal fin is fan-shaped. The anal fin is also elongated and pointed and is located on the underside of the fish. The pectoral fins are located on the sides of the body, near the gills.
Molly fish have a unique coloration that varies depending on the morph. The most common color morphs include black, silver, gold, and albino. The wild-type molly fish is typically a silver color with dark spots along their sides. The males typically have a more vibrant coloration than the females. Some color morphs have a metallic sheen, giving them an iridescent appearance. The fins can be transparent or have a different color than the body. For example, a black molly might have transparent fins while a golden molly may have orange fins. The females are usually larger and rounder than the males and have a small black spot in front of their dorsal fin, which is known as the “gonopodium.”
In addition to their color morphs, molly fish also have various finnage types. These include short-finned, long-finned, and sailfin. The short-finned variety is the most common and the easiest to find in pet stores. Long-finned and sailfin varieties are less common and require more specialized care. These varieties have longer fins that can be easily damaged or torn. They are also more sensitive to water conditions and require a more stable environment.
Lifespan
Mollies have a lifespan of about 3-5 years in captivity.
Size
Mollies typically grow to be about 2-4 inches in length.
Tank Size Requirement
A minimum tank size of 20 gallons is recommended for keeping mollies. It’s important to note that because mollies are livebearers, they should be kept in a tank with enough space for them to swim and also for the fry to have a place to hide.
Water Parameters
Mollies prefer a pH of 7.0-8.0 and a water temperature between 72-78°F. It’s important to keep the water clean and well-filtered as mollies are sensitive to poor water quality.
Diet
Mollies are opportunistic feeders and will eat a variety of food such as flakes, pellets, frozen and live food such as brine shrimp, bloodworms, and daphnia. Vegetable matter should also be included in their diet, such as blanched spinach or lettuce. Reference the table below for a more exhaustive list of foods you can consider feeding your Mollies.
| Food for Mollies | Description |
|---|---|
| Flakes | Commercial fish food |
| Pellets | Commercial fish food |
| Frozen brine shrimp | Nutritious frozen food |
| Frozen bloodworms | Nutritious frozen food |
| Daphnia | Small, freshwater crustaceans |
| Vegetable matter | Blanched spinach or lettuce |
| Algae wafers | Commercial fish food |
| Live brine shrimp | Nutritious live food |
| Live bloodworms | Nutritious live food |
| Live daphnia | Nutritious live food |
| Live black worms | Nutritious live food |
| Live tubifex worms | Nutritious live food |
| Live mosquito larvae | Nutritious live food |
| Live Grindal worms | Nutritious live food |
What to Put in Their Tank
Mollies do well in a planted tank and can be kept with other peaceful fish species. Mollies will eat algae and appreciate the addition of some live plants in their tank. It’s also recommended to include hiding spots and caves for them to retreat to.
Common Diseases
Here are the six most common diseases that molly fish are susceptible and you should consider investigating if you notice sick fish:
- Ich (Ichthyophthirius multifiliis): Ich is a parasitic infection that causes small white spots on the skin and fins of the fish. This is caused by a protozoan parasite that attaches to the fish’s skin and gills. The spots can be treated with a commercial ich medication, but the tank must be treated for several days to ensure that all the parasites are eliminated.
- Fin Rot: Fin rot is a bacterial infection that causes the fins of the fish to become frayed and ragged. This is usually caused by poor water quality or an injury to the fins. Fin rot can be treated with a commercial fin rot medication, but the water quality must also be improved to prevent reoccurrence.
- Swim Bladder Disease: Swim bladder disease is a condition that affects the swim bladder, causing the fish to have difficulty swimming. This can be caused by poor water quality, overfeeding, or an injury. Swim bladder disease can be treated with a commercial swim bladder medication, but the water quality must also be improved to prevent reoccurrence.
- Velvet Disease (Oodinium): Velvet disease is a parasitic infection that causes a golden or rusty colored dust to cover the fish. This is caused by a dinoflagellate parasite that attaches to the fish’s skin and gills. The disease can be treated with a commercial velvet medication, but the tank must be treated for several days to ensure that all the parasites are eliminated.
- Columnaris (Flexibacter columnaris): Columnaris is a bacterial infection that causes cotton-like growths on the fish’s skin and fins. This is usually caused by poor water quality or an injury. Columnaris can be treated with a commercial Columnaris medication, but the water quality must also be improved to prevent reoccurrence.
Behavior & Temperament
Mollies are generally peaceful fish and are well-suited for community tanks. They are active swimmers and enjoy the company of their own species.
Tankmates
Here is a large list of ideal tankmates you might consider adding to your Molly tank:
| Molly Tankmate | Description |
|---|---|
| Neon tetras | Small, brightly colored fish |
| Guppies | Livebearers with vibrant colors |
| Swordtails | Livebearers with a unique tail shape |
| Platies | Livebearers with a variety of colors |
| Corydoras catfish | Peaceful bottom dwellers |
| Ghost shrimp | Transparent shrimp that help keep the tank clean |
| Harlequin Rasboras | Small, active fish |
| Cherry barbs | Small, active fish |
| Otocinclus catfish | Small, peaceful catfish |
| Zebra Danios | Active, schooling fish |
| White cloud mountain minnows | Hardy, small fish |
| Panda corydoras | Peaceful bottom dwellers |
| Bamboo shrimp | Unique, freshwater shrimp |
| Amano shrimp | Large, algae eating shrimp |
| Red cherry shrimp | Brightly colored, small shrimp |
| Ghost catfish | Peaceful, nocturnal fish |
| Siamese algae eaters | Efficient algae eaters |
| Bristlenose pleco | Peaceful, nocturnal fish |
Breeding
Mollies are livebearers and will breed readily in captivity. It’s important to have a separate breeding tank with a pH of 7.0-7.5 and a water temperature of 78-82°F. It’s also important to have hiding spots for the fry, as the adult mollies will eat them if given the opportunity.
Morphs
Here is a list of colorful morphs to consider that your local fish shop likely do not carry. You can find these morphs online from retailers and breeders that specialize in breeding Mollies.
| Morph Name | Description |
|---|---|
| Sailfin Molly | The sailfin molly is a variety of molly fish that is known for its large dorsal fin. This morph comes in a variety of colors, including black, silver, and gold. |
| Dalmatian Molly | The Dalmatian molly is a variety of molly fish that is known for its distinct black spots on a white body. |
| Lyretail Molly | The lyretail molly is a variety of molly fish that is known for its unique tail shape, which is similar to a lyre. |
| Black Molly | The black molly is a variety of molly fish that is known for its solid black coloration. |
| Silver Molly | The silver molly is a variety of molly fish that is known for its shiny silver coloration. |
| Balloon Molly | The balloon molly is a variety of molly fish that is known for its rounded body shape that makes it look like a balloon. |
| Gold Dust Molly | The Gold Dust Molly is a variety of Molly fish that is known for its unique golden spots on a black body. |
| Leopard Molly | The leopard molly is a variety of molly fish that is known for its leopard-like spots on the body. |
| Green Molly | The Green Molly is a variety of Molly fish that is known for its green coloration. |
| Neon Molly | The neon molly is a variety of molly fish that is known for its bright neon coloration. |
| Ghost Molly | The ghost molly is a variety of molly fish that is known for its transparent body with visible internal organs. |
| Cobalt Blue Molly | The cobalt blue molly is a variety of molly fish that is known for its deep blue coloration. |
| Lavender Molly | The lavender molly is a variety of molly fish that is known for its pale purple coloration. |
| Crimson Molly | The crimson molly is a variety of molly fish that is known for its deep red coloration. |
| Candy Stripe Molly | The candy stripe molly is a variety of molly fish that is known for its multicolored stripes. |
| Albino Molly | The albino molly is a variety of molly fish that is known for its white and pink coloration. |
| Piebald Molly | The piebald molly is a variety of molly fish that is known for its distinct white spots on a dark body. |
| Lace Molly | The lace molly is a variety of molly fish that is known for its intricate lace-like patterns on the fins. |
| Chocolate Molly | The chocolate molly is a variety of molly fish that is known for its dark brown coloration. |
| Wild Type Molly | The wild type molly is the original, natural coloration of molly fish found in the wild. |
| Marble Molly | The marble molly is a variety of molly fish that is known for its unique marbled patterns on the body. |
| Coral Red Molly | The Coral Red Molly is a variety of Molly fish that is known for its deep red coloration on the fins. |
| Blue Cream Molly | The Blue Cream Molly is a variety of Molly fish that is known for its blue and cream coloration. |
| Blue Diamond Molly | The Blue Diamond Molly is a variety of Molly fish that is known for its diamond shaped blue spots on the body. |
History and Origin
The history and origin of the molly fish can be traced back to Central America and Mexico. They are a freshwater species that are native to the warm and tropical regions of these countries, where they can be found in slow-moving streams, rivers, and canals. Mollies are known to inhabit a wide range of environments, including brackish waters and even some coastal areas.
The species was first described by the German naturalist and explorer Alexander von Humboldt in 1821. He named the species Poecilia sphenops, which translates to “small wedge-shaped fish.” The species was later reclassified by the Dutch ichthyologist Pieter Bleeker in 1853 and grouped under the genus Poecilia, which includes all livebearing fish such as guppies and swordtails.
The species was first introduced to the aquarium hobby in the mid-19th century, and since then it has become one of the most popular freshwater fish species kept in home aquariums. This is due to its hardiness, ease of care, and a wide range of colors and patterns available. In the wild, the molly fish is known for its hardiness and adaptability, and this trait has been passed on to the captive-bred varieties.
Mollies have been selectively bred for decades to produce different colors, patterns and fin types, which has led to the creation of many different morphs and strains. The most popular color morphs are the sailfin molly, black molly, silver molly, and the Dalmatian molly, but many more are available (see the Morph section for a larger list).
In recent years, molly fish have also been used in scientific research due to their ability to adapt to different environments and their ease of breeding in captivity. Studies on mollies have provided insights into evolution, genetics, and reproductive biology.
Today, mollies are widely available in pet stores and online, and they continue to be a popular choice among fish keepers of all levels of experience. This species is considered a hardy and adaptable fish that is easy to care for and maintain, making it a great addition to any freshwater aquarium.
Frequently Asked Questions
Q: How often do molly fish need to be fed? A: Molly fish should be fed small amounts 2-3 times a day. Overfeeding can lead to water quality issues and health problems for the fish.
Q: What is the ideal water temperature for molly fish? A: Molly fish prefer water temperatures between 72-82°F (22-28°C)
Q: How do you tell the difference between male and female molly fish? A: Male molly fish typically have longer dorsal fins and are smaller in size compared to the female. Female molly fish have rounder bellies and shorter dorsal fins.
Q: Can molly fish live in brackish water? A: Although molly fish are able to tolerate a slight increase in salinity, they are not considered a true brackish water species and should not be kept in water with a high salinity level.
Q: Can molly fish be kept with other species of fish? A: Molly fish are generally peaceful and can be kept with other peaceful species of fish such as tetras, platies, and swordtails.
Q: How can I tell if my molly fish is pregnant? A: Female molly fish will have a round belly when they are pregnant.
Q: How long does it take for molly fish to give birth? A: The gestation period for molly fish is approximately 4-6 weeks, after which the female will give birth to live fry.
Q: What should I do if my molly fish gives birth but the fry disappear? A: It’s possible that the fry have been eaten by other fish in the tank or have not been noticed. To avoid this, it is best to separate the adult fish from the fry after birth.
Q: How often should I perform water changes for my molly fish tank? A: It is recommended to perform a water change of at least 25% once a week to maintain optimal water quality for your molly fish.
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