Are Mollies Hardy? What That Makes Them Hardy??

Mollies are a type of freshwater tropical fish. They are “the other goldfish” because they look similar to the common goldfish, but mollies can live in saltwater and freshwater environments. A lot of people had the misconception that these fish are not very smart or interesting. As this fish is gaining popularity, people are curious about questions like: Are Mollies hardy? What Makes Them Hardy?

Yes, Mollies are hardy fish that can handle most water parameters as long as they have enough oxygen, space, food, and clean fresh water, so it’s best not to set their tank up with anything more than your typical water conditioners.

We will explore the shady nature of Mollies in this post. Hopefully, you will enjoy it.

Are Mollies Hardy?

Mollies are hardy fish, making them the perfect choice for beginners and those who have trouble maintaining water parameters. Mollies make great tank mates in communities with other small or medium-sized species of fish that prefer similar temperature ranges. It is important to remember that this fish needs an aquarium set up with plenty of space and decor and an efficient water filter system.

What Makes Mollies A Hardy Fish?

Mollies are hardy fish. This is because they can live in a wide range of environmental parameters. Besides this, some reasons that make Mollies a hardy fish are:

  • They can tolerate a wide range of water parameters. They can live in tanks with high pH, soft or hard water, and low temperatures up to 15 degrees Celsius. This means that they can survive when the tank’s ammonia levels fluctuate as long as there is still some nitrite level available for them.
  • Mollies are not picky about their tank mates. Even if they come from different families like the Cichlids or Tetras, they can live with other fish species with similar water parameters, such as low pH and nitrite. As long as there are various plants to hide from predators, Mollies can live in the tank with other fish species.
  • They are hardy when it comes to their food as well. Omnivorous by nature, they will survive on various foods such as flakes, pellets, and vegetables, making it easier for novice aquarists to take care of without worrying about what food to feed.
  • Mollies are quite hardy in their water parameters because they can live in tanks with low nitrate levels, high ammonia or nitrite levels, and even a fluctuating pH level as long as there is still some hardness available for them. This means that the tank owner will not need to worry about the water parameters fluctuating as long there is still some hardiness available for them.

What Happens If The Water Parameters Fluctuate?

If your tank has some fluctuations in the water parameters, it’s not a big deal. This is because Mollies are hardy fish that can survive through changes in environmental conditions. However, if you noticed that one of the water parameters had increased too much, you should take measures to try and bring it back down. For example, if the pH is high or there’s an ammonia spike, you can change partial tank water to bring things back into balance.

This is a common problem that many fish keepers are not aware of. If the water parameters fluctuate, it will affect your molly’s health, and they can feel stressed out and unhealthy. Therefore, it is good to know what causes fluctuations in the first place so you can better prevent them from happening or treat it accordingly if it does happen.

Which Tank Is Best For Mollies?

Mollies are a great fish for beginners because they are easygoing. They don’t require much space, and their water requirements are low as long as you keep the tank clean. This makes mollies perfect first-time starter fish. However, many people find it difficult to maintain Mollies to pick out what kind of tank works best for them.

There are many different kinds of tanks to choose from, but you should consider the water parameters of Mollies. Thus, the best tanks for Mollies are:

  • Tanganyikan tanks have hard water of 136 ppm and pH levels around eight to nine. This will provide the Mollies with an environment rich in minerals, ions, and trace elements like calcium, potassium, magnesium, copper, etc.
  • Tetra AquaArt aquariums are perfect for mollies because these tanks have a hard water level of 125 ppm and pH levels around eight to nine.
  • Aquaclear filters are also good for mollies because these filters produce an environment that is rich in minerals, ions, and trace elements like calcium, potassium, magnesium, copper, etc.

How Does Water Parameter Contribute To Make Mollies Hardy?

Water parameter is an essential element that you should take into account for Hardy Fishes. The water parameters, such as pH, hardness, alkalinity, and temperature, can affect the Hardy Fish’s health and make it hardy.

General Hardness In Mollies

General hardness (GH) is the amount of calcium and magnesium ions dissolved in water as carbonates, bicarbonates, or other compounds. It indicates how well a fish can tolerate variations in pH due to acid rain or other factors which alter the balance between alkalinity and acidic substances. It also affects the mineral content, and you can express them in degrees of hardness.

General Hardness levels for Mollies should be around 125-175 ppm (parts per million). If you don’t know your water parameters or where to test them, call a local fish store that will help answer these questions.

Temperature And Hardy Mollies

The optimal temperature for mollies is (24-29) degrees Celsius or 75 to 82°F. The higher the temperature, the more oxygen they need, so make sure you keep them in a well-aerated tank with a high water turnover and plenty of space to swim around.

Mollies are happy at room temperatures but will do best in the range between 24 and 29 degrees Celsius or 75 to 82°F. The higher the temperature, the more oxygen they need, so make sure you keep them in a well-aerated tank with a high water turnover and plenty of space to swim around.

pH Makes Mollies Hardy

The pH level of the water is a critical factor that determines if mollies are going to be hardy or not. Mollies can survive in tanks with pH levels between six and nine, but they will do better when on the lower side of this range. The reason for this is because ammonia becomes less toxic at a lower pH level. However, mollies like the water to be closer to seven, so you should keep it within that range if possible.


Nitrate is a crucial parameter for mollies. High nitrate levels can lead to algae blooms and low oxygen content in the water, which would eventually cause fish death. They are also very toxic to the fish. Therefore, the nitrate level in a tank should be as low as possible and below 20ppm for mollies, which is not too hard to achieve with regular water changes.

If you have a saltwater tank, then nitrates will be higher because of how marine life lives and what they produce as waste products in their environment. However, freshwater fish will have lower nitrates than saltwater because of the processing of waste products and a lack of plants to process them.

In both cases, it would be best to check on ammonia levels before doing anything else since that can sometimes cause an increase in nitrate levels if there’s a problem with the nitrogen cycle in your tank.

Exceptions About Water Parameters For Mollies

Undoubtedly, Mollies have great adaptability in most of the water parameters, but there are some exceptions. Such as:


Nitrite is also present in the water. It is a byproduct of nitrates after breaking into nitrogen gas. This could be lethal to fishes if levels were high enough. So levels should not exceed 0.25 mg/l for hardy fish like Molly fishes, too, and make sure you rarely do some water changes and clean the filter at least once a week to minimize this parameter.


Ammonia is a chemical compound that can be present in the water, and it is toxic to fishes. A level of ammonia should not exceed 0.25 mg/l for hardy fishes like Molly fish. If you find that your ammonia levels are higher, make sure you do some water changes to help reduce or remove the high ammonia levels.

What Happens If The Water Parameters Fluctuate?

If the water parameters fluctuate in the tank, it will not be good for Hardy fishes. It will cause problems with disease and stress levels and make it difficult to keep a stable environment for them. They need stability and consistency to thrive when other factors are less consistent or stressful, which happens if water parameter fluctuations happen.

Moreover, some problems of fluctuation of water parameters in fishes are:

  • Lack of oxygen
  • An increase in ammonia and nitrite
  • Difficulty with pH balance and alkalinity
  • Producing ammonia which is toxic for fish.
  • Cause fluctuations in other parameters like pH, carbonate hardness, and temperature

It is important to maintain a stable environment to prevent fluctuations. This includes having the right number and type of fish, a proper feeding schedule, an appropriate tank size with room for adequate filtration, etc., so that fishes can live happy and healthy lives.

What Causes Fluctuation In Water Parameter?

There are several reasons for fluctuations in the water parameters, such as changes in nitrate levels due to improper feeding or stress from other fish that produce more ammonia than usual. The key is being aware and knowing what triggers these problems so you can anticipate them before they actually occur.

However, some of the causes of fluctuation in water parameters are:

  • Frequent feedings
  • Too many fish for the size and space in your tank
  • Poor pH level, causing a buildup of new carbonates
  • Temperatures too high for fish
  • Lack of water change
  • Age of the tank
  • Poor circulation due to filter not working properly

The general rule is that if you change your water once a month and feed your fish just as often, fluctuations in parameters should be minimal.  

Best Tank Mates For Mollies As A Hardy Fish

Mollies are hardy fish and will do well in most average tanks. Although these fishes prefer to live in smaller tanks, having companions with them will help maintain the water parameters. Some fish that are best tank mates for Mollies include:

  • Guppies
  • Platys
  • Swordtails
  • Corydoras Catfish

Guppies can do well with most fishes and are not so aggressive, which is good for Mollies. Platys are one of the best tank mates because they can live in smaller tanks and don’t do well with bigger fishes like Cichlids. Probably eating them up when placed into their aquariums. Swordtails generally follow the “live and let live” motto, making it ideal for a tank mate. Corydoras Catfish is also one of the best tank mates for Mollies because they can live in small tanks and don’t do well with bigger fishes.

Tank Enemies For Mollies As A Hardy Fish

Don’t fall under the calmer appearance of molly fish. This fish does have some enemies that they don’t allow in their tanks.

So, the tank enemies of mollies are:

Other fish

You cannot keep other fishes with mollies. These fish will eat them, which would lead to their death over time, like the Siamese fighting fish, the guppies, the feeder goldfish, and other fishes from different species.

Larger Fish

Larger fishes like goldfish will scare away mollies because they are too big for them and might even eat them. This can cause a lot of stress in their tanks, leading to death over time, such as Clown Loach, Plecostomus, Catfish, and other large fishes.


Since mollies are live fish with plants in their tanks, it’s better to avoid putting them near any following plants. Over time, they can cause stress or death: Anubias Nana; Java Ferns; Sagittarius Canadensis (Java Moss).


These are also enemies for mollies that live in the tank since they have much food from their leaves. And this can be a problem for them because they will lose their food source.

Decorations that Are Too Big

Don’t put decorations in the tank that is too big since they make it difficult to swim. Also, this is not good for your mollies, as they need to have space to maintain healthy fish.

“Big” Objects

The different objects in the tank should not be too big for mollies. This can also make it difficult to swim and restrain their movement with these obstacles around them. To maintain this rule when you are decorating your tank so that they don’t have any difficulties swimming or finding food.


Summing up, Mollies are hardy fish. But you need to keep them inside the house in the right tank with water parameters that match their needs. If you want to make sure your mollies stay healthy and happy for years to come. Try our special guide on what makes mollies so tough. It contains all of the information you need about general hardness, alkalinity, temperature, pH level, and nitrate content. As well as some tips on how best to maintain these values. We also have included an extensive list of tank mates and enemies. It will help you decide if this is the perfect type of fish for your situation.