Melafix Betta Fin Rot

Melafix For Betta Fin Rot: Is This The Best Option?

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At, we’ve become well-accustomed to writing articles about fin rot! Because it’s one of the most common ailments of domestic betta fish, many people try to treat it with medications.

While Melafix or Bettafix are two of the most popular choices, they’re also quite controversial. There have been many reports of betta fish dying or reacting adversely to these meds that contain Cajeput oil.

Let’s explore these medications further to understand where the problems lie.

Key Takeaways

  • Betta fin rot can sometimes be successfully treated with Melafix and Bettafix, but in other cases, they appear to react adversely and may even die.
  • Although it hasn’t been proven, some people believe the essential oils in the medication interfere with the labyrinth organ in betta fish.
  • Luckily, there are plenty of effective alternative treatments including improving water quality, adding aquarium salt, and Indian almond leaves.

What Is Fin Rot?

Fin rot is a bacterial or fungal infection (Aeromonas sp., Pseudomonas sp., or Vibrio sp.) that affects fish fins and sometimes, other areas of flesh. Usually, this results in weak, tattered fins that eventually start to tear and disintegrate.

In most cases, fin rot is caused by poor water quality that weakens your betta’s immunity, and provides a perfect breeding ground for bacteria that invite infection.

For most hobbyists, the treatment for fin rot is as simple as keeping up with complete clean water changes and improving water conditions. However, for more extreme cases, stronger treatment is recommended.

One of the most commonly recommended medications is Melafix or Bettafix, though some believe that these products do more harm than good for your betta.

What Is Melafix?

API MELAFIX Freshwater Fish Bacterial Infection Remedy 16-Ounce Bottle
  • Contains one (1) API MELAFIX Freshwater Fish Bacterial Infection Remedy 16-Ounce Bottle
  • Heals bacterial infections and repairs damaged fins, ulcers and open wounds
  • Contains natural, botanical tea tree extract to quickly and rapidly help fish


Melafix claims to be an all-natural treatment containing 1% cajeput oil. Very similar to tea tree oil, cajeput oil is derived from the same Melaleuca or ‘honey myrtle’ genus.

While tea tree oil has been used for centuries as a form of medicine, this cure-all isn’t always reliable for betta fish.

Potential Problems of Melafix and Betta Fish

The problem with using Melafix to treat your betta is that your betta fish has a labyrinth organ.

This lung-like organ allows betta fish to breathe atmospheric air in case water conditions and dissolved oxygen levels deteriorate.

However, it’s long been said that tea tree oil and other similar essential oils will cover the labyrinth organ, making it difficult for fish with labyrinth organs to breathe. Some hobbyists even think that a layer of Melafix at the top of the water will impede the ability to breathe.

Many of these claims come from the fact that the fish owner administered a dose of Melafix, and the fish died within minutes, making it seem like the medication was the problem. But is this a direct result of the Melafix?

There are a couple of reasons why this might have happened instead:

Your Betta Fish Was Already Dying

When fish become sick, they are very susceptible to changes in water parameters. A small fluctuation in temperature or other parameters can be enough to kill your betta fish if they’re already too far gone.

This could potentially be the same case with a betta fish that has been treated with Melafix.

As mentioned before, medications are only recommended in extreme cases and are often seen as a last resort for treating fish disease and illness.

If your betta fish was already too far gone and you treated it with Melafix, there is a possibility that the change in water conditions stressed out and killed your fish and not the actual medication.

You Overdosed the Medication.

Melafix has been widely available in the hobby for years and experts have perfected the correct dosage to treat disease and illness.

The recommended normal dosage for Melafix is 5 ml per 10 gallons (37.9 L); remember that only 1% of this is actually essential oil.

Unfortunately, many hobbyists are desperate to try to save a dying fish. If treatment is done incorrectly, this can mean overloading the system with several medications.

Even though you’re not directly administering the medication as you would for other animals, the treatments will start to harm the betta fish in excess concentrations.

Not only will this create additional stress that your weak fish might not be able to regulate, but it can also create other internal problems that can quickly lead to death or permanent damage.

Adhere to the dosing instructions, and this can easily be avoided.

What Is Bettafix?

API Bettafix Betta Medication - 1.7 oz (93B)
  • Contains one (1) API BETTAFIX Antibacterial & Antifungal Betta Fish Infection and Fungus Remedy 1.7-Ounce Bottle
  • Heals bacterial infections, repairing damaged fins, ulcers, and open wounds and promotes regrowth of fins
  • Treats newly introduced fish to reduce risk of disease outbreak and heal wounds and tissue damage

But what if you use Bettafix? This medication is designed specifically for bettas, so it must work, right?

Well, there’s actually a lot of controversy around Bettafix, too! To understand it more, we need to look at the ingredients.


Bettafix is very similar to Melafix but less concentrated.

This medication is an all-natural antibacterial that contains 0.2% cajeput oil as opposed to the 1% that Melafix has.

Even in smaller concentrations, hobbyists still believe that the oil can cover the fish’s labyrinth organ, making breathing difficult and leading to an untimely death.

Fact vs. Fiction

The debate on Melafix and Bettafix is ongoing.

Not many studies have been made to prove that tea tree oil detrimentally affects breathing, but hobbyists keep losing fish.

If you’re worried about dosing these medications, try other treatment methods first. While these treatments might be more time-consuming and less effective in emergency cases, they’re the safest and most proven ways to treat fin rot.

If you’re left with no other options, and it’s truly a life or death situation, then Melafix or Bettafix could be a final resort. Just make sure that you follow the instructions carefully to avoid any chance of overdose.

The Best Ways To Treat Fin Rot

Luckily, there are many other ways to treat fin rot safely with little to no additional costs. In my opinion, it’s always best to attempt treatment of mild health conditions with good aquarium maintenance before resorting to medicine.

The best ways to treat fin rot are:

  • More water changes and higher water quality
  • Aquarium salt
  • Indian almond leaves
  • Increased aeration
  • Maracyn, Waterlife Myxazin, and Kanaplex medications

It is usually best to start with more natural treatments and progress to medications if the infection is mild enough. In more severe cases, you may wish to go straight to medications.

To further understand how fin rot works and how to treat it, make sure to check out Betta Fish Fin Rot: Causes And Cures.


Melafix and Bettafix are notorious in the aquarium hobby for treating betta fish with the common disease known as fin rot.

While they might be labeled as all-natural due to their tea tree oil content, it is said that these oils can cover the labyrinth organ, making breathing difficult for your betta fish.

However, other hobbyists suggest that betta death after dosing Melafix or Bettafix is usually just an untimely death resulting from overdosing.

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