United by their popularity as beginner aquarium fish, both mollies and guppies share the same family and habitat. While they have similar diets, reproductive strategies, and water condition requirements, they vary widely in size and appearance.
Given their distinct looks, it’s not unusual to wonder whether you can house mollies and guppies together in a tank and if they get along. As a beginner aquarium enthusiast, this is a reasonable concern that reflects your desire to keep your pet fish safe and healthy.
In this article, we’ll answer that exact question and offer more information about how mollies and guppies should be kept.
Table of Contents
Do Mollies and Guppies Get Along?
To say it plainly, yes, mollies and guppies can be housed together in a sufficiently large tank with proper care and tank set-up. Being from the same family and similar habitat, mollies and guppies share critical tank requirements that you need to maintain to sustain an optimum environment suitable for them both.
However, before you go stock your tank with mollies and guppies, let’s discuss the level of care you need to deliver to help them have a fulfilling life.
Also be careful to not overstock it as both species are active swimmers and need non-competitive, open spaces to thrive.
Molly and Guppy Overview, Lifespan, and Habitat
Mollies are live bearing freshwater fish, popular due to their vibrant colors, peaceful temperament, and relative ease of care. There are several molly breeds, including the common molly, sailfin molly, dalmatian molly, balloon molly, and lyretail molly, that are common in aquariums worldwide.
With proper care and nutrition, mollies can easily live for 3-5 years in a home aquarium. In the Central American canals, lagoons, and mangroves, however, their lifespan drastically reduces due to predation.
For guidance on selecting the perfect tank size, check out our detailed article here.
Mollies
| Information Chart | Molly |
|---|---|
| Scientific Name: | Poecilia sphenops |
| Family: | Poeciliidae |
| Care Level: | Easy |
| Temperament: | Peaceful |
| Color: | Various colors including black, white, orange, silver, and gold |
| Lifespan: | 3 – 5 years |
| Size: | 3 – 4 inches |
| Diet: | Omnivore (flakes, pellets, and live/frozen foods) |
| Minimum Tank Size: | 20 gallons |
| Temperature: | 70 – 82F |
| WaterConditions: | pH 7 – 8.5 Moderate water hardness |
| Tank Mate Compatibility | Compatible with peaceful fish, including guppies. |
Guppies
Guppies, aka rainbow fish or millionfish, are another live-bearing freshwater fish in the Poeciliidae family similar to mollies. They are one of the most popular aquarium fish globally, known for their vibrant colors in males, which also have elaborate fins.
A bit shy of the lifespan of mollies, guppies generally live for 2-3 years in well-maintained aquariums, giving birth to tens of fry; even if separated from the male. Guppies originated from the northeast South American ponds and slow-moving streams, but they’ve now found their way to many global freshwater habitats.
| Information Chart | Guppy |
|---|---|
| Scientific Name: | Poecilia reticulata |
| Family: | Poeciliidae |
| Care Level: | Easy |
| Temperament: | Peaceful |
| Color: | Various colors and patterns including red, blue, green, yellow, and mixed |
| Lifespan: | 2 – 3 years |
| Size: | 1.5 – 2.5 inches |
| Diet: | Omnivore (flakes, pellets, brine shrimp, daphnia, and vegetables) |
| Minimum Tank Size: | 10 gallons |
| Temperature: | 72 – 82F |
| Water Conditions: | pH: 6.8 – 7.8 Moderate water hardness |
| Tank Mate Compatibility | Compatible with mollies. |
Molly and Guppy Appearance
Mollies are known for their vibrant colors and come in a wide variety of breeds, each with unique characteristics. Most species of mollies have a stocky, torpedo-shaped body with a rounded bell and they typically grow to be 3-4 inches long, with females being slightly larger than males.
Their fins come in various shapes and sizes depending on the breed, with the large dorsal fin of the sailfin molly and the elongated tail fin of the lyretail molly being very popular among aquarists. In the wild, mollies have a dull silvery color. However, captive-bred mollies showcase a dazzling array of colors, including black, white, yellow, orange, red, and even metallic shades with some breeds having spotted or marbled patterns.
Guppies, on the other hand, are much smaller. They have slender, elongated bodies with males being slimmer than females. Guppies are relatively small fish, typically growing to 1-2 inches in length. The females are slightly larger than the males.
The fins are a key distinguishing feature of guppies, especially in males. Male guppies have elaborate fins, particularly the caudal and dorsal fin, which boast dazzling colors, patterns, and shapes. Females have shorter, less colorful fins.
Guppies come in a stunning array of colors—more diverse than mollies—including red, blue, green, yellow, orange, purple, and even metallic shades. They often have a combination of these colors and intricate patterns on their bodies and fins.
Discover the top fish choices for your pond setup in our comprehensive guide here.
Mollies and Guppies Care and Tank Set-Up
As mentioned, mollies and guppies can share a tank with proper optimization of tank parameters. Here’s what you need to know about their tank requirements:
Tank Size and Specification
When setting up a tank for guppies and mollies, it’s crucial to consider their specific needs to ensure a healthy environment. Here are the tank size and specification details that you need to ensure:
Optimum Tank Size
While some sources may suggest a minimum of 15 gallons for smaller species like common mollies, a 20-gallon tank is a better starting point for mollies. They are active swimmers and appreciate some space to explore and play around. For larger molly breeds like the sailfin molly, a 30-gallon tank or bigger is recommended.
Guppies, however, are smaller and can thrive in a 10-gallon tank. However, for a thriving community tank with mollies, a 20-gallon tank is ideal.
Filter Type
Both mollies and guppies produce a moderate bioload. A good quality hang-on-back (HOB) filter or canister filter is suitable. Choose a filter rated for a tank size larger than your actual tank to ensure efficient filtration.
However, ensure that your filter is rated for the tank size. Or else, it may suck in the small fishes.
Substrate
Although mollies are considered bottom feeders, both mollies and guppies aren’t substrate-dependent to a great extent. In case you don’t want to go with the bare-bottom option, choose a medium-sized gravel that is smooth to avoid injuring their fins. Sand can also be a good choice if you can ensure proper water flow to avoid stagnant areas.
Water Parameters for Mollies and Guppies
Both mollies and guppies are adaptable fish, but providing the right water parameters will ensure their optimal health and vibrant colors.
Water Temperature
Although mollies prefer slightly warmer water, the ideal range of water temperature to keep mollies and guppies is between 72°F – 82°F (22°C – 28°C). Use a reliable heater and thermometer to maintain consistent temperature.
In the summer, increase surface-level water flow and keep the tank covered indoors, ensuring the maintenance of proper temperature.
Water Flow Rate
A moderate water flow is preferred by both mollies and guppies. Adjust the filter output or add a powerhead to create good water circulation but avoid strong currents. Observe your fish. If they are struggling to swim against the current, adjust the flow rate accordingly. Introduce flow restrictors, such as a sponge or a PVC flap, to further reduce the flow rate.
pH
While they both can tolerate a wide pH range, a slightly alkaline pH of 7.0 to 8.2 is accepted by mollies and guppies. Monitor your pH levels regularly with a test kit to ensure consistency.
- To raise pH: Add aragonite substrate or crushed coral to your tank. These slowly buffer the water and increase its alkalinity.
- To lower pH: Use driftwood or peat moss in your tank. These release tannins that can slightly acidify the water. However, be cautious with driftwood as it can also impact water hardness. Learn effective ways to naturally lower your aquarium’s pH for healthier fish. Read our guide here.
Water Hardness
Mollies prefer moderately hard water in the range of 8-12 dGH, while guppies are more adaptable and usually do well in a similar environment. Monitor the water hardness with a test kit to safely keep your fishies.
- To increase hardness: Add aragonite substrate or crushed coral to your tank.
- To decrease hardness: While not typically necessary for mollies and guppies, if your water is extremely hard, you can perform water changes with RO/DI water or use a commercial product specifically designed to soften aquarium water. However, be cautious with sudden changes in hardness.
Mollies and Guppies Tank Landscape
Creating an interactive and explorative environment for your mollies and guppies is key to their well-being. Here are some ideas for plants, decorations, and lighting:
Best Plants for Your Tank
Live plants are considered best for mollies and guppies tanks. They provide hiding spots for the fry, in addition to improving water quality. Some excellent choices for mollies and guppies may include:
- Java Fern: This low-maintenance fern thrives in low to moderate light and can be attached to driftwood or rocks.
- Hornwort: This fast-growing plant provides excellent cover for fry and helps control algae growth.
- Water Sprite: This easy-care plant grows quickly and helps maintain good water quality.
- Amazon Sword: This popular plant comes in various sizes and adds a touch of elegance to the tank.
- Guppy Grass: As the name suggests, this fine-leaved plant is a favorite hiding spot for guppy fry.
Worst Plants for Your Tank
Avoid plants with sharp edges or thorns that could injure your fish, especially the delicate fins of guppies. Furthermore, if you’re not planning on setting up a high-tech lighting system, avoid plants with high light requirements.
Decorations for Your Tank
Some decoration choices for guppies and mollies may include:
- Driftwood: Driftwood adds a natural look to your tank and can help buffer the water slightly, making it more acidic. However, carefully choose driftwood that has been cured for aquariums to avoid affecting water quality.
- Rocks: Rocks can provide hiding places for your fish and create interesting aquascapes. Ensure the rocks are smooth to avoid injuring your fish.
- Caves and tunnels: Caves and tunnels offer hiding spots for shy fish and breeding mollies. Filed and smoothed PVC pipes also make excellent caves.
Lighting for Your Tank
A full-spectrum lighting system that simulates the natural day-night cycle is considered best for guppies and mollies. Moderate lighting for 12-14 hours a day promotes growth and excellent coloration in guppies, live plants, and mollies.
Feeding Mollies and Guppies
Both mollies and guppies are omnivores, meaning they thrive on a diet that includes both plant and animal matter. Here’s a breakdown of the best diet for them:
Best Diet for Mollies and Guppies
High-quality flake food should be the staple of the diet of mollies and guppies. Consider formulations that are designed for tropical fish and are small enough for their mouths. High-quality pellets can also be a good alternative to flakes, especially for mollies, as they tend to be more bottom feeders.
Live food like brine shrimp, bloodworms, and daphnia is a great occasional treat for both mollies and guppies. It provides them with essential protein and variety in their diet. Occasionally, both mollies and guppies enjoy blanched vegetables like spinach, zucchini, or cucumber—introducing vitamins and fibers to their diet.
How often should you feed them?
Overfeeding is a common problem with small aquarium fish like guppies and mollies. Feed your fish only what they can consume in 2-3 minutes, two times a day for adults and 3-4 times a day for fry. Uneaten food can decompose and pollute the water.
Behavior and Temperament
Considered beginner-friendly, mollies and guppies are generally peaceful fish that can be good tank mates for each other. Here are some more details about their behavior and temperament:
Guppies
- Guppies are schooling fish and thrive in groups of their own kind, ideally with a ratio of more females to males. This helps reduce aggression among males who compete for females’ attention.
- Guppies are energetic and enjoy exploring all levels of the tank. Provide them with ample swimming space and hiding spots.
- While generally peaceful, males can be aggressive towards each other, especially in a tank with limited space or too few females. They may also nip at the fins of slow-moving or long-finned fish like sail-finned molly.
Mollies
- Mollies are generally peaceful fish, but like guppies, males can be aggressive towards each other, especially when competing for females.
- Mollies also can sometimes nip at the fins of slow-moving or long-finned fish like guppies.
- Mollies are active swimmers but tend to spend more time in the middle and lower parts of the tank.
Common Diseases and Their Treatment
While generally hardy fish, mollies and guppies also are susceptible to a few freshwater fish diseases. Here are some of them discussed:
Ich (White Spot Disease)
Caused by a parasitic protozoan (Ichthyophthirius multifiliis) that attaches to the fish’s body and gills. Common symptoms include small white spots appearing on the body, fins, and gills. Your fish may flash against objects in the tank and rub their bodies.
Raising the tank temperature slightly (within safe limits for your fish) and using a medication specifically designed for Ich are acceptable treatment methods. Consult your vet in extreme cases.
Fin Rot and Tail Rot
This is caused by bacterial or fungal infections that damage the fins and tail. Often developed due to stress or injury. Frayed, discolored, or rotting fins and tail are the primary symptoms.
Clean the tank thoroughly and frequently perform water changes to improve water quality. Use an aquarium medication specifically for fin or tail rot. In some cases, moving the affected fish into a hospital tank for treatment may be necessary.
Swim Bladder Disease
A malfunction of the swim bladder causes this issue. The swim bladder is the organ that helps fish maintain buoyancy. This can be caused by various factors like bacterial infection, overfeeding, constipation, or internal injuries. If affected, your fish might struggle to swim properly, appearing to be floating upside down or having difficulty staying upright.
The usual treatment involves fasting the fish for a few days and ensuring pristine water quality. Epsom salt baths can sometimes be helpful in mild cases. In severe cases, consult a veterinarian specializing in fish.
FAQs
Yes, you can put mollies and guppies together as they share similar water parameters and temperaments. However, be careful with fin-nipping behavior, and don’t overstock the tank.
Mollies can be extremely aggressive even towards their own if subjected to an overstocked tank or bad water conditions. However, in suitable conditions, mollies and guppies coexist pretty comfortably.
Both mollies and guppies are great beginner-friendly fish that require comparatively less maintenance. If space is a concern, you can stock more guppies in a similar tank than mollies.
The Bottom Line
Hopefully, you’ve now got your answer to whether mollies and guppies get along or not. They can be housed together in a reasonably spacious tank with proper tank parameters and nutrition without any issues. All the best!