Are Essential Oils Safe For Fish?

Essential oils safe for fish - fish swimming with essential oils in the foreground

By Mark Piatt

Updated on June 15, 2021

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Updated June 2022

Since many people use essential oils on themselves and sometimes their pets to treat various conditions, you may be wondering if essential oils are safe to use on fish or around fish.  Since I am a tropical fish owner and I use a wide variety of essential oils in my diffusers, I was wondering the same thing.  After doing some extensive research and from my real-life experiences, I have learned some essential oils can be used to treat various fish conditions.


Information provided in this description is for educational purposes only.  For possible treatments of physical or mental diseases, please seek a trained and licensed health professional.  Enchanted Aromatics is not responsible for any adverse side effects resulting from the use of any suggestions, products, preparations, or procedures mentioned or from following historical uses of essential oils.

Can essential oils be used to treat fish for various ailments?

First, fish are remarkably diverse creatures. Because of this, what may be safe for one fish may be detrimental to other types of fish.  As an example, many people have tropical aquariums in their homes that may have a variety of fish, including a catfish.  If your fish get an external parasite, fungus, or even some bacterial infections, one of the most effective treatments to use is potassium permanganate (if used properly.)   But if you have catfish in your aquarium, this treatment can potentially kill them.

But some essential oils can be used on some fish to treat a variety of ailments and maybe even as a preventative measure. 

Sitting on the desk that I am writing this article on is a 15-gallon hexagonal plexiglass aquarium that holds about a dozen adult guppies (when the darn things are not breeding), 1 glow tetra (I had 7 but 3 were killed from a bacterial infection and the rest died of old age) 1 peppermint pleco that I never see (hides in his rock cave), some snails and miscellaneous plants. 

* Since writing this article last year, I have not had any more infections.  I now have 6 glow tetra, 7 guppies, and my 30-year-old pleco.

Plexiglass aquarium sitting on a deskI had replaced my fluorescent aquarium light with LED lights but was dealing with black algae bloom because of the lighting change.  About a month after I replaced the lights, I noticed a small white hairy-looking spot around the mouth of one of my glow tetras.

It quickly spread and started on a second fish.  I realized I was most likely dealing with Columnaris (cotton mouth), which is a deadly, fast-acting bacterial infection caused by a gram-negative bacteria known as Flavobacterium columnare. 

There are several essential oil-based fish products you can use for treating various fish ailments.  In my case, for treating the bacterial infection, I successfully used the following product:

Imagitarium Bacterial Remedy

  • Natural anti-bacterial alternative to harsh medications
  • Non-toxic for aquatic life, environmentally friendly formula
  • Does not color water
  • Safe for live plants
  • Active ingredients: Citrus, Eucalyptus, Neem, Cinnamon

I was a little concerned about treating the fish with a product that used essential oils, especially for the pleco (he/she is about 30 years old).

Fish gills are sensitive and essential oils are powerful.  Imagine sucking on a cinnamon toothpick.  Very hot! 

For this reason, I do not like adding the product directly into the aquarium.  I will mix it in a 32 oz. container filled with water, and then pour that in.  

I started with 1/3 the recommended dosage so I could keep an eye on the pleco.  When it appeared, that the pleco could tolerate the medication, I increased the dosage.  I landed up losing 3 glow tetras, but 4 that also had the infection survived.  After about a week, there was no sign of the infection.   

I can say that at least guppies, glow tetras, and a pleco can tolerate citrus, eucalyptus, neem, and cinnamon if used in the correct doses.  This combination appears to have cured them of Columnaris.

There are other essential oil-based products for treating various fish ailments.

Now I have not personally used the following product, but it does get good reviews.  76% are 5-star and 13% are 4-star ratings.  Overall it receives a 4.6 out of 5.0.  

For treating freshwater fish that are suffering from fin and tail rot, open red sores, open body wounds, eye clouds, pop eye, body slime, and mouth fungus there is the following product:


  • All-natural treatment containing botanical tea tree extract to quickly and rapidly help fish
  • Heals bacterial infections & repairs damaged fins, ulcers & open wounds
  • Helps treat newly-introduced fish to reduce the risk of disease outbreaks in freshwater aquariums

But as for using essential oils on other fish, I can not say if essential oils are safe to use.

Be sure and pay attention to any expiration dates or pay attention to how long you have had the product.  Different essential oils have different shelf lives.  Citrus-based oils have the shortest shelf life – about 1 year.

Scientific studies for treating fish with essential oils

There are plenty of published studies that show how certain essential oils have anti-fungal and anti-microbial properties.  But I have been unable to locate a single study that involves treating fish with essential oils.  But I have compiled a short list of studies that look at the antifungal and antibacterial properties of essential oils.

  1. Activity of Various Essential Oils Against Clinical Dermatophytes of Microsporum and Trichophyton 

The study looked at 65 essential oils and 25 essential oil blends.  They mainly tested against dermatophytes from two primary genera – Microsporum and Trichophyton.  16 species were included in the study.  Researchers found that overall, all species and strains with a genus, Microsporum showed a 28.6% inhibition at 21 days.  Trichophyton showed inhibition of slightly over 20%.  Strain-to-strain differences were also observed. 

  1. Sensitivity of Candida albicans to essential oils: are they an alternative to antifungal agents 

This study used 12 essential oils against 30 different vaginal strains of Candida albicans.  The study found that Candida albicans are more sensitive to certain essential oils compared to commercial drugs used to treat this pathogen.  The essential oils mainly disrupted the cell walls and membranes of the yeast.

  1. Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties 

This article discusses the various antimicrobial properties of tea tree essential oil.  It concludes that there is a “wealth of in vitro data now supports the long-held beliefs that TTO has antimicrobial and anti-inflammatory properties.”  Many more clinical studies need to be conducted to demonstrate tea tree essential oil’s ability to control these microbes. 

  1. Antifungal effects of citronella oil against Aspergillus niger ATCC 16404 

The study found that citronella can completely kill Aspergillus niger.  This study concluded that citronella oil has the potential of being a safe and environmentally safe fungicide.

Essential oils that are safe for fish

Keep in mind that there are too many fish species and too many variables to accurately say which essential oils can be used on fish.  But the following list of essential oils has reportedly been safely used on some fish.

OrangePalo SantoPeppermint
RosemaryTangerineTea Tree

Essential oils that are toxic to fish

Although this is not a comprehensive list, these are some of the more popular essential oils that have been reported that should not be used with your fish.  Keep in mind that it may largely depend on the specific species of fish.  For example, this list includes cinnamon as being toxic to fish.  Yet, the first product we mentioned and that I used on my fish includes cinnamon.

Angelica AniseBasil
Bergamot Birch Calamus
Celery SeedCinnamonCistus
FennelFir (All Variants)Grapefruit
MarojamMountain SavoryMyrtle
OreganoParsleyPenny Royal
Tea TreeThujaThyme
WintergreenYarrowYlang Ylang

You may notice some essential oils are on both lists, such as citronella myrtle, and orange.  Again, some essential oils may be safe on some fish but not others.  There have not been any comprehensive studies on this subject, most of the information available is subjective or anecdotal. 

What is the proper amount of essential oil to use on your fish?

Since each fish and each essential oil is different, that is impossible to answer.  Essential oils can be made up of hundreds of compounds.  Many essential oils even have artificial compounds added to them.  Since essential oils are derived from plants and are unregulated, many different things can affect the quality of essential oils including soil, climate, geographical region, pollination, methods of extraction, temperature, fertilizers, pesticides, adulteration, method of storage, age, etc.

Consistency in essential oils is impossible to achieve.  Because of this, it is impossible to know what is safe for what fish and in what quantities. 

Some sites report to dose your aquarium with essential oils, use a toothpick dipped in the oil, and then dipped in the aquarium.  My problem again is that each essential oil is different.  Also, a toothpick of essential oil dipped into a 5-gallon tank is different compared to dipping it into a 100-gallon tank.  Some sites report you can use 2 -5 drops for every 10 gallons of water.  But again, each essential oil is different, and each fish is different.

My advice?  Unless it is a product made specifically for fish (such as the one I used to treat my fish with a bacterial infection), I would not treat my aquarium with essential oils.  In this case, I much prefer to use traditional treatments. 

Signs that your essential oils may be harmful to your fish

Drawing of 3 colorful fish in waterIf you do wish to treat your fish with essential oils, you will need to carefully observe them for any distress.  If you observe any of your fish in distress, you need to immediately do a large water change (20% – 50%), maybe even a second water change.  But remember, water changes can also stress out your fish. 

Here is a list of signs to look out for:

  • Gasping at the surface or the bottom of the tank
  • Erratic or lethargic behavior or fast changes in speed
  • Color changes
  • Spotting or dark marks appearing on the body

Other things to look out for when using essential oils in your aquarium

Keep in mind that oil floats on water.  Since fish receive their oxygen by a transfer of oxygen at the surface.  The oil may block this transfer from occurring. 

A healthy fish tank needs a healthy equilibrium of bacteria to break down fish and plant waste.  Essential oils may disrupt this equilibrium with their antimicrobial properties.  This may result in algae blooms, nitrate or ammonia build-ups, or bacterial infestations. 

Can I use my essential oil diffuser around my fish tank?

Looking around the internet and different forums, you will find some people who say it is safe to use your diffuser around your aquarium and others who vehemently oppose using a diffuser around your aquarium. 

I do not know what the final verdict is, but I can say that I have been using a diffuser around my tropical aquariums for years, and I have not observed any ill effects. 

With that said, I never have my diffuser right next to my aquarium, but I do sometimes have my diffuser on the other side of the desk where my office aquarium lives (in a small bedroom). We have a 30-gallon aquarium in our den, and it is also regularly exposed to a diffuser, with no ill effects.   I have also used all the main types of essential oils and many of the lesser-known essential oils.    

Perhaps there are some species of fish that cannot tolerate essential oils, even in the most minute quantities, but my fish do just fine.

Can I use essential oils in my acrylic fish tank?

The fish tank I mentioned at the beginning of this article is an acrylic tank that I have had for over 30 years.  I see no problems with the tank from using essential oils.  

You do not want to store essential oils in a plastic container, since it is reported that some essential oils can break down some plastics. 

But since the amount you are using in your aquarium is so diluted, I doubt it should cause any problems to your acrylic –  at least that has been my experience.  Also, I see no ill effects to my tubing, power filter, nothing.

I have an article that goes into greater depth about plastic and essential oils if you are interested.  Is the Plastic in Essential Oil Diffusers Toxic?

This article also discusses the types of plastic that can be used with essential oils.

Final Verdict

As a fish owner, I do not like to add any chemicals to my aquariums.  But sometimes, fish get sick and need a helping hand.  I am usually more inclined to use tried and true treatments versus experimenting with my fish.  But I have found that using that one product I mentioned earlier, definitely seems to have cured my fish of their ailment. 

If you wish to use essential oils to treat your fish, I suggest you stick with commercial products that use essential oils that have been specifically formulated to be used on fish.  I would hope these companies that sell these products vet their suppliers. 

I believe that relying on random essential oils is playing with fire when treating your fish.  There are just too many variables and not enough information out there to justify treating your precious fish with these unknowns – other than the few products that have been formulated to be used on fish.

Don’t start using random essential oils on your fish to see what effects the essential oils have on your fish.  

Your fish friends can not tell you when they are in distress. 

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