What Diseases Do Molly Fish Get?: Prevention And Treatment

Molly fish are one of the most popular fish in the world. They are famous for their adorable, round bodies and beautiful colors. What many people do not know is that Molly fish can get diseases just like other animals. The answer is not many, but these occurrences can be deadly for them.

What are the most common illnesses that affect Molly fish? What Diseases Do Molly Fish Get? To give you an idea of what might happen if your pet gets sick, here’s a list of some illnesses that may cause problems:

  • Ammonia Poisoning
  • Dropsy
  • Fin Rot
  • Fungal Infections (such as White Spot)
  • Flukes (Trematodes)

In this article, we will look at some of the diseases that these cute little creatures might come across.

Are Molly Fish Susceptible To Diseases?

Molly fish is one of the most sensitive fish in the aquarium, and they are very susceptible to diseases. They have scales damages quickly. So it is important to include many hiding places because this will make them feel protected from their enemies.

Besides this, they are also susceptible to the quality of water that they have in their tank. If the water quality is not optimal, Mollies will quickly get sick and also die.

What Makes Molly Fish Prone To Diseases?

Mollies are one of the most popular fish in home aquariums. However, what makes Molly fish prone to diseases is their need for a specific temperature range. Thus, it would be best if you kept them in a tropical temperature between 74˚F – 82˚F (23 ̊C-28 ̊C). Additionally, they require salt levels of at least one tablespoon per five gallons (18.93 l) of water, preventing certain diseases that occur from poor water conditions.

Mollies will eat just about anything (including feces). They often live in already sick tanks with other animals who may be ill or dead. It makes an environment for disease to spread like wildfire, mainly if Molly eats parasite-infected animals.

When Mollies are in a tank with aggressive fish, they often feel stressed, making them more liable to diseases.

Mollies get several different parasitic infections, one of the most common things that will cause these fish to die early.

What Diseases Do Molly Fish Get?

Molly fish are pretty and popular. They get a lot of attention, but they can be pretty easy to take care of, at least in the short term.

In addition, they are great beginner fish, making it even more important to understand what these beautiful creatures need to stay healthy and happy. Let’s look at some of the most common health problems with this type of fish and learn how to avoid them.


Fluke transfers through an internal parasite in the fish from the water in their tank. Flukes attach themselves to the gills, fins, and body of a Molly Fish and suck out their blood, causing damage. It’s widespread with these types of fish because it can be hard to see signs of fluke infestations until you know the fish are acting differently.

Mollies are more likely than most other types of fish to have flukes. Therefore, you must treat them if they get them by adding a treatment to their water or using the medication as recommended on package instructions.

Prevention: Many people will flush out the water in an aquarium where a fish has had flukes and replace it with fresh water. Make sure to keep on top of maintenance as usual.

Fungal Infection

One of the most common diseases that Molly fish get is a fungal infection or tail rot. It occurs due to too much exposure to uneaten food or even high levels of nitrates in the water, which create an environment where fungus can flourish.

Prevention: The good news is that this disease is pretty easy to treat. All you need to do is remove these fish from the water and clean their tails with hydrogen peroxide.

Swollen Gills

The gills of Mollies often swell. It is a sign of stress and illness in the fish, which happens because they cannot breathe properly due to excessive mucus that accumulates on their gills. If you notice this problem with your pet mollies, immediately remove them from water and clean out their tank, as cleaning will help remove the mucus and restore their breathing.

Prevention: Maintain optimum water conditions in the tank by using a good quality filter. Frequent cleaning of the aquarium is necessary to prevent the accumulation of organic waste material, which may cause stress to mollies.

Fin Rot

Mollies are particularly susceptible to fin rot that occurs due to bacteria. It starts with a small part of the fins damages. Then, it slowly spreads until the disease affects much of their tail.

Fin rot can be fatal if you do not treat them quickly. So make sure to look for any signs as soon as possible. The most common symptom is a ragged fin and white or transparent lesions, which usually appear on the tail.

Prevention: There are a few things you can do to prevent fin rot. The first is keeping the water clean and warm; it should be at least 75 degrees Fahrenheit. It will help fight off bacteria, which thrive in colder temperatures. You also need to feed your fish with fresh food and remove any uneaten portions after only two minutes have passed or so.

Ammonia Poisoning

Ammonia poisoning is a common problem, especially in smaller tanks. This type of poisoning occurs when the fish release ammonia through their gills into the water. In small amounts, these toxins are not harmful to Molly fish. But it can build up quickly and prove fatal if you don’t take care of them.

Prevention: While there isn’t much you can do to prevent ammonia poisoning, maintaining a clean tank is the best way to avoid it. It means changing out the water regularly and cleaning your filter often.

Dropsy Disease

Dropsy disease occurs when parasites in a fish’s gills or digestive system release toxins into its body, causing fluid to build up under its scales. Symptoms include bulging eyes, scales that stick up and out from the body, sunken eyes, or a bloated appearance.

Prevention: This is most common when you keep fish in a plastic container. So, it is best to use a glass tank with robust filter systems. You can prevent it by properly caring for your tank and only keeping Molly’s fish together if they are of similar size to avoid bullying issues.

Fish Fungus

Fish fungus is a highly contagious bacterial infection. It causes white or gray spots on the body, fins, and scales of your Molly fish that soon spread to their eyes as well.

Prevention: Treatment for this illness requires antibiotics. So it’s important you take your pet to a veterinarian if you suspect he has contracted this disease.

Swim Bladder Disease

The swim bladder is the most common problem among fish. The swim bladder, which controls buoyancy in the water, expands and contracts as your pet breathes. But when it’s over-inflated or under-deflated, it can cause all sorts of problems, including difficulty swimming and staying upright.

Prevention: Keeping your tank at a typical depth can help prevent this issue from occurring in the first place. If you are noticing signs of swim bladder disease, it’s best to take your fish to an aquarium professional for treatment as soon as possible.

Fish Lice

Fish louse looks like small white dots crawling around on the body of your fish. They are incredibly contagious and transmits from one fish to another during feeding or through contact with the tank walls.

Prevention: Fish louse often transfers between fish by human hands. So you should always handle fish gently if at all, to avoid spreading these parasites. The best way to prevent fish lice is to avoid overcrowding your tank and keeping the water clean, so you can spot them early and treat them with an insecticide.


Ich is a common and highly contagious fish disease that causes white spots to form on their fins, scales, or gills. This illness can be fatal if you fail to treat them as quickly as possible.

Prevention: Don’t keep your pet in an overcrowded tank, and make sure you check for signs of ich regularly to treat it before it spreads.

How To Treat The Diseases Of Molly Fish?

Many things could happen to the fish in your aquarium. But there is one thing you always need to be especially careful with, and this is the disease of the fish. It is important to be aware of what diseases your fish could catch because it will help you treat them early when they are still curable and how reliable the treatment methods are for each disease.

Some treatment methods for the diseases of Molly fish are:

Salt Bath

Molly fish are tropical freshwater fish. So it would help if you treated them with salt when they have diseases. This is because the salt helps heal their wounds. It can also kill some of the bacteria that cause disease in fish. To make a salt bath, you should add about one teaspoon per gallon of water or enough for the fish to take in.

The best time for a salt bath is during the morning or night because this will not stress out your molly fish too much. It will also make them less likely to get sick again after treatment.


Some medications can help treat the diseases of Molly fish. But it would help if you were very careful which pill you choose because some medicines can kill your fish.

Always check if the medication you want to use is compatible with the kind of water you have in your aquarium. Also, ask an expert before using it.

Proper Diet And Feeding Schedule  

Mollies need a proper diet and feeding schedule so they can stay healthy. For one, you should feed them small portions of food twice a day and never overfeed them or leave food leftovers in the aquarium because this can cause water pollution.

Mollies are omnivorous, so they need an equal amount of plant and animal-based food in their diet. So, always make sure that they get enough vegetables like cucumber and zucchini. These foods will help fight your fish fight against diseases caused by parasites.

How To Keep Molly Fish Healthy?

Molly fish have some special needs to make sure they stay healthy. For example, they are susceptible to water conditions and temperature, requiring a little attention and more space than other fish.

So, you must keep the aquarium clean at all times, change 25% of the water weekly (or 50%, depending on how many Molly’s there are), and make sure the pH level of the water is between 7.0 and 8.0. The temperature should be 24-28 degrees Celsius (75 to 82 Fahrenheit).

Besides this, they need filters to make sure the water is clean and oxygenated. They also need some hiding places, like plants or rocks, so they can avoid other fish that might hurt them. Mollys are very peaceful creatures. But when bigger fish chase them (or even humans), they tend to jump out of the aquarium.

Proper lights are also important for a healthy environment. Make sure the plants have enough light to get oxygen and absorb nutrients. Also, it is essential to provide them hiding places and preventing Molly fish from exposure to direct sunlight.

Don’t forget to feed Mollies with flakes and pellets. And to remove the uneaten food after a few minutes to avoid water pollution or bacterial growth.

There you go! These simple tips should help your Mollys stay happy and healthy.


In this article, we’ve discussed the most common diseases that affect mollies. Although, these are not all the possible disorders or illnesses that can show up in your fish tank. You should take them seriously and treat them as soon as you see any symptoms of the disease. Even if it seems like a minor problem, don’t wait because it can become a big problem.

Do you have any questions about your fish? Or want to share some experience with other owners. Please leave us a comment in the section below! We always appreciate hearing from our readers.