The Ultimate Molly Fish Care Guide

Are you thinking about getting a Molly Fish as a pet?

They’re cute and have personality, plus they’re easy to care for… right? Not so fast.

While Molly Fish are easier to care for than some other fish, there are still some things you need to do to make sure your Molly is healthy and happy.

In this guide, we’ll cover everything you need to know about Molly Fish care.

Molly Fish Origin

Poecilia sphenops is a fish species in the genus Poecilia, commonly known as molly; it is also known as short-finned molly or common molly.

These species are members of the Poeciliidae family, and they inhabit freshwater streams as well as saltwater coastal, brackish, and marine environments throughout Mexico, Colombia, and other Central American countries.

Author note: Guppy fish are considered to be in the same genus as Poecilia.

For several years, it had been noticed that the guppy might breed with the mollie under specific conditions, and the close genetic link between the two had been verified.


Molly fish come in a number of hues, forms, and patterns.

The majority of them are about 3.5 to 4.5 inches long, with flattened bodies and short fins.

Different types of mollies have different appearances:

  • Black mollies: The Black Mollies (the most prevalent molly fish species) have black bodies with rounded fins measuring three to six inches in length.
  • Sailfin mollies: They’re small fish with gray bodies and dark gray spots, as well as a big, puffy dorsal fin that looks like a boat sail.
  • Dalmatian mollies: These species have rounded fins and gleaming, silver-white scales encrusted with black spots, they resemble the Dalmatian dog breed.
  • Balloon mollies: They have balloonlike bodies with colors ranging from white, silver, black, orange, and yellow.
  • Lyretail mollies: The caudal fins of these fish taper into sharp points at the top and bottom, and trail behind them as they swim.

Care Level

Mollies are quite common because of their adaptability.

They’re really simple to keep, making them an excellent gateway into the aquarium world for novices.

They are mostly freshwater fish, although they can survive in seawater if necessary due to their flexibility.

However, just like other fish species, molly fish have different care requirements that you need to understand.

In the subsequent parts of this article, you will learn more about those requirements so you can provide them with a healthy and safe environment for them to live in.

Water Parameters

1. Water Cycling

When it comes to mollies, everyone seems to agree that water changes must be done on a regular basis.

Mollies have a high bioload, so weekly water changes (25-30% changes) are necessary to keep the water column clear of pollutants and rejuvenate the tank’s water.

2. Water Temperature

Mollies are native to freshwater estuaries that have a normal water temperature range.

So, providing these species with a tank temperature that ranges from 72 to 78 degrees Fahrenheit (22 to 25.5 degrees Celsius) is ideal.

3. pH Level

Although every molly has its own specific water pH preference, most mollies require a constant environment and hard water.

In general, the ideal molly pH level is 7.5 to 8.5.

Note: Many hobbyists who have softer water need to keep crushed coral in the tank to help buffer the water.

Tank Setup

1. Tank Size

Mollies are tiny in size, they can survive in small and medium-sized aquariums.

A general rule of thumb, the majority of molly fish may live happily in a tank as little as 10 gallons.

However, that tank size suggestion is appropriate for up to four mollies, if you have a bigger family, it’s nice to have a larger tank since bigger is always better.

Note: The sailfin molly is the only species that need a larger tank because of its size.

These fish are somewhat larger than your common molly, therefore they will need a bigger aquarium to avoid stress.

A tank with a capacity of 30 gallons or more is ideal for sailfin types.

2. Tank Heater

As previously said, Mollies are a versatile fish, but the ideal temperature to keep them happy is between 72 and 78 degrees Fahrenheit (22 and 25.5 degrees Celsius).

This implies if you live in regions that do not consistently achieve these temperatures throughout the year, you will need to invest in some effective heaters for your Mollies.

However, if you already live in a place that maintains hot climates, you shouldn’t provide extra heating to your fish, just be sure to use a good filtration unit.

3. Tank Filter

Mollies are hardy fish, they don’t require as much filtration as other fish need, and can survive in a variety of environments.

However, filters are important for two reasons:

1. Dirty water can affect mollies’ growth process.

2. They need a balanced amount of oxygen in the tank

For your molly fish, a water pump, air stone, or anything else that provides oxygen to the water is beneficial.

When oxygen concentrations in the aquarium decrease, these fish frequently congregate at the surface of the tank and try to grasp some fresh air.

Therefore, you’ll need to increase oxygen exchange so that enough enters the aquarium and meets your molly fish’s demands.

4. Tank Lighting

While mollies do require some specialized aquarium care, they generally don’t require intense lighting.

Mollies, on the other hand, will benefit from having live plants in their aquarium; live plants need strong illumination – and other attention – to grow.

As a result, while mollies themselves may not require strong lighting, their ideal aquarium most certainly would.

For example, in a fish-only aquarium, you only need enough light to view your mollies; 1 watt of lighting power per gallon of aquarium volume is often adequate to see your fish.

For tanks larger than 50 gallons, you should probably increase this to 2 watts per gallon to allow for greater depth.

However, tropical aquariums require more light: anywhere from 1.5 to 5 watts per gallon, depending on the type of plants you wish to maintain.

You should also give them a photoperiod–the length of time the lights are on each day–of 8 to 12 hours as tropical fish.

5. Tank Decoration

Natural decor that replicates the natural rivers mollies live in in the wild is ideal for mollies.

This implies adding a lot of plants and locations to hide.

Also, add sand or gravel substrate at the bottom of your tank.

Mollies spend the majority of their time in the middle and upper regions of the water column, so they won’t mind this environment at all.

In fact, aragonite sand can be beneficial to molly because it releases minerals into the water.

It’s also important to add taller plants like Anubias, as well as shorter kinds such as Java fern.

When you arrange the plants, place them along the aquarium’s perimeter so that there is still open swimming space.

Finally, finish off the look with some pebbles, caves, and driftwood.

Those things will provide additional shelter while also supporting algae growth in your mollies’ tank.

Tank Mates

If you want to establish a multi-species tank, you have a lot of choices.

Mollies get along with just about everything!

If the other tank mates are docile, mollies will not have any difficulties interacting with them.

Just avoid fish that have been known to be aggressive since larger fish might boss or even attempt to consume your molly.

Also, try to maintain similar-sized fish in your aquarium.

Here are some excellent tank companions for the molly fish:

  • Cherry Barb
  • Swordtail Fish
  • Dwarf Gourami
  • Celestial Pearl Danio
  • Rosy Barb
  • Bristlenose Pleco
  • Cory Catfish
  • Zebra Loach
  • Platies
  • Most Types Of Tetras
  • Harlequin Rasbora
  • Yoyo Loach

Diet and Feeding

In the wild, this species feeds on invertebrates, plants, and algae.

This makes maintaining their diet in captivity simple because it is not difficult to replicate this diet in your tank.

They are also called tank cleaners since they consume algae.

This means that they will assist you to keep the tank’s conditions stable and will require less upkeep on your part.

To match the diet of these fish in your tank, try feeding blanched veggies like lettuce and spinach.

And for the protein part of their diets, look into maintaining bloodworm and brine shrimp.

Frozen foods are another good and simple choice to feed your mollies, but feeding them live food might spice up their mealtimes and improve their natural scavenging abilities.

How much should you feed them?

Mollies are little creatures, so you need to put in your mind that they eat little meals.

If they don’t finish their meal within a two-minute, then you need to clean the tank and cut off the amount the next time.

As a rule of thumb, they don’t have to feed too often; twice a day is sufficient.


Researchers have conducted mating preference tests in different environments on the molly fish.

What’s interesting about the mollies is that they gestate their young differently than other fish.

Mollies are livebearers, which means they don’t lay eggs.

What the females do is allow their eggs to grow inside them before being discharged.

These species are simple to breed in captivity and will do so on a regular basis if you plan to breed molly fish.

However, the aquarium’s condition is something that you should be concerned about.

Everything must be perfect for mating to occur.

And to stimulate mating, your mollies’ aquariums need to be clean and the water temperature must be sufficient.

Depending on the usual temperature you maintained it at, we recommend raising it by a few degrees or so, but not more than 10 degrees Fahrenheit above the normal range.


Tetras are very sensitive to polluted water and they will show signs of stress and illness when the quality of your tank’s water changes or when it becomes too polluted.

The following are the four most frequent diseases that affect tetras:

Molly Disease

The illness is named after mollies because it affects them so frequently.

If your mollies get molly disease, you will observe that they become less active and perform unusual motions, such as wiggling.

If your mollies begin to exhibit these behaviors, it’s time to check the water quality. It’s not difficult for aquarium fish to recover from molly sickness.

They’ll be delighted and live comfortably once the water conditions have returned to normal.


The majority of freshwater fish are affected by Ich, caused by the protozoan Ichthyophthirius multifiliis.

The disease is characterized by white spots that resemble salt sprinkles on the fins, body, and tail of the fish. Fish with Ich appear sluggish and grind against rough surfaces.

To treat Ich, move the sick fish to a quarantine tank with warmer water (by two degrees) and add one tablespoon salt per five gallons of water in the tank.


Another frequent molly disease is velvet, which is caused by a parasite known as Oodinium.

The parasite digs into the fish’s skin and creates gold, rust-like cysts.

Molly fish with velvet will dart about the tank from one end to the other, appear listless, and rub against rough surfaces.

To cure velvet, turn off all lights in the tank and add copper sulfate, acriflavine or formalin according to your veterinarian’s instructions.

Fin and Tail Rot

Long-finned mollies and mollies with fan-like tails are prone to fin rot and tail rot.

This infection is caused by a bacterial infection acquired due to overcrowding, low-quality water, and stress.

A molly fish afflicted with fin rot will have frayed, ragged, and milky-colored fins.

To treat fin and tail rot, do a complete water change, as well as use antibiotics if the fish’s symptoms do not improve within one week.

Last Words

Mollies are great and very rewarding fish.

Their beauty and intelligence in the tank make them a wonderful addition to your family.

Just remember to provide them with the care and patience they deserve.

We hope you enjoyed this article as much as we did.

If you still have any questions, please share them with us in the comment section below.