Can Fish Eat Mint? Is it Safe? [What Does Science Say]


You bought a bunch of mint from the supermarket and wondered if you could feed it to your pet fish. Cheap and easy! As strange as it might sound, fish can eat mint, but with exceptions.

Fish can eat mint but only in small amounts, it is not the main food in their diet, and only after testing. Mint commonly used to feed fish are pennyroyal (Mentha pulegium. L.), Corsican mint (Mentha requienii), peppermint (Mentha piperita), and water mint (Mentha aquatica).

Let’s read more about it.

Feeding Mint To Aquarium Fish – Safe? What Science Says

The menthol in mint tends to repel many animals such as deer and small burrowing animals. Mint leaves can taste strong to fish. If your fish is able to consume it in small amounts or in extract form and added to their regular food, they will be alright and will even thrive.

I will discuss 2 research studies where fish has been actually fed with mint to support this statement plus a bonus study that shows mint can benefit fish and not only be used as a once in a while dietary supplement.

Which type of Mint Fish Can Eat? – Infographic

Research #1

The first study is research on the effects of feeding mint (Mentha arvensis) to common carp (Cyprinus carpio). This was conducted to see if mint can be a viable solution for controlling fish diseases in aquaculture production.

In the study, the mint leaves were subjected to processes that allowed the researchers to obtain the mint extract. The extract was then mixed into the regular fish meal.

The study yielded the following results:

  • An increase in the values of the carp’s red blood cell and hemoglobin count.
  • The fish were free from infections and diseases.
  • That the mint extract did not cause anemia to the fishes.
  • That mint extract can be a viable natural immunostimulant/dietary supplement for cultured fish.

Research #2

The second investigated the effects of using peppermint (Menta Piperita) as a dietary supplement on the growth of rohu carp (Labeo rohita). The researchers measured “growth” as a) weight gain, b) growth rate and c) food conversion ratio.

The study was also conducted to see if it would benefit aquaculture which has in recent years become a huge food production sector. Due to the production demand in aquaculture, many owners have resorted to using antibiotic dietary supplements to fish.

The problem with this is that antibiotic residues accumulate in the fish tissues and the evolution of microbes that are resistant to antibiotics. Hence the drive from many researchers to experiment on herbal supplementation.

The study was able to observe the following on fish fingerlings: a) positive effect on all the “growth” parameters on all the fish, b) no mortality during the experimentation period, c) a triggered appetite.

Bonus Research

The third study is not about dietary supplementation with mint. It is about investigating whether the use of essential oils from clove, mint, and camphor could be an effective anesthetic for clown anemonefish (Amphiprion ocellaris) in confinement conditions during transportation.

I will only talk about the effects of the mint on clown anemonefish. In the study, the researchers diluted the essential oils with 100% ethanol prior to application. Then the fishes were exposed to different concentrations of mint extract in water.

Observations were done and data were taken at different hours to record the stages of anesthesia the fish were in. The study drew the following conclusions:

  • Mint extract lessened the detrimental effect of confinement on clown anemonefish during transportation therefore it is a viable anesthetic.
  • The most effective mint extract concentration was 25 µL per liter.
  • The optimum fish density is 10 fishes per liter.

What Fishes Eat Mint?

From the research we found (not many, unfortunately), these are the fishes that were used in mint supplementation experiments:

  • Barramundi or Asian sea bass (Lates calcarifer),
  • Caspian white fish (Rutilus frisii kutum),
  • Common carp (Cyprinus carpio),
  • Tambaqui (Colossoma macropomum).

You will notice that these are fishes grown for food production. Despite not having any clear scientific evidence to back this up, I can infer that mint supplementation will work on your aquarium fish when you use mint extract mixed with fish food or pellet-type feed mixed with mint powder.

If you want to go this route, this was how the experimental diets were designed according to the 2 studies discussed above:

  1. In Research #1, the fish were fed two times a day with fish food mixed with mint extract at an unspecified percentage. The feed amount was 3% of the fish’s body weight.
  2. In Research #2, weight gain was the highest in fish fed twice a day with feed that is 5% of its body weight. The fish food was mixed with 2% of peppermint powder.

Clearly feeding mint to fish for supplementation is something that needs careful consideration. I have not even mentioned the fish tank conditions in both experiments. To make it simple, you can try it yourself in microdoses and then gradually increase the amount over time.

Why Use Mint Extract Instead Of The Essential Oil?

You might be wondering why in the 2 experiments discussed above the mint essential oil was in diluted form or what is called “extract.” This is because essential oil is 4 times stronger than extracts and will cause harm to the fish.

Mint extract is obtained by either a) soaking mint leaves and stems in alcohol or b) by watering down the essential oil with alcohol. On the other hand, pure essential oil is obtained by exposing mint leaves and stems to high temperatures.

Can I Put Mint In The Fish Tank?

Many pet fish owners have actually tried this idea and discovered that their mint plants and fishes were thriving. Aquarium plants are fully submerged but mint as a terrestrial plant should only be partially submerged.

If you’ve decided to use mint in your fish tank, there are 3 vital things to remember:

  • Only submerge half of the roots;
  • Pruning the lower leaves so that no leaf could ever touch the water;
  • Branches must also stay above water;
  • Trimming the roots regularly.

Why should the leaf never touch the water? Mint can cause harm to the fish in 5 ways: 1) Irritation, 2) Oxygen depletion, 3) Indirect water contamination 4) roots filling up the aquarium, and 5) nitrite spike.

1 – Irritation

Mint leaves contain a higher concentration of menthol and when this compound gets released into the water, it would irritate or burn the gills and mucous membranes of the fish. Indeed, it can be safe for ingestion but not for being absorbed through the gills.

Think about eating yogurt. It is safe when you eat through your mouth but not through your nose!

2 – Oxygen Depletion

When the mint dies, the essential oils from the leaves will leech into the water. This can lead to a limiting of gas exchange in the water and so reducing the level of oxygen available for the fish to breathe.

3 – Indirect Contamination

If pesticides were used in the garden and on the mint plants and there was residue left on the leaves, it can cause water toxicity. If a chemical eliminates pests, it can eliminate fish.

Mint Aquarium Garden

4 – Roots Filling Up The Aquarium

Roots should be regularly trimmed especially in smaller fish tanks so it doesn’t fill the tank making it difficult for fish to swim in.

Fishes love to hide and rest between the roots. When they do that, they end up receiving microdoses of essential oils from the mint. This is not something to get worried about.

The fish actually benefits in that the essential oil will protect them from helminth parasites from contaminated feeder fishes. More on feeder fishes later.

5 – Nitrogen Spike

When mint or any other dying or decaying plants are left in the aquarium, it causes a nitrogen spike.

Plants in the state mentioned above create ammonia. The ammonia breaks down into nitrite, causing a nitrogen spike in the fish tank. These chemicals are poisonous to the fish and any other live organisms in the aquarium.

Can Fish Eat Herb-based Turtle Pellet Food?

This question often comes up often from those who are new to raising both a fish and a turtle in one aquarium. The answer is, it depends on what type of fish you have. Is your fish a 1) carnivore, 2) herbivore, or 3) omnivore?

If it’s a carnivore, it will obviously not be a good idea to have herb-based food as its main diet. However, a few amounts of plant-based feed from time to time will not harm the fish.

Carnivore diet should contain lots of protein. A good solution is getting your turtle a commercial feed that has lots of protein and provides them a separate serving of vegetables.

1 – Carnivores

A few examples of carnivore fish are: pipefish, betta fish, Arowana, piranha, cichlids, and killifish. Fishes like these are natural predators and when in the wild they feed on other fishes, crustaceans, and small amounts of plant matter.

Feeder Fishes

As I have mentioned earlier, carnivores require a protein-rich diet made of between 45 and 70% of protein. Many pet stores sell commercial live fish food such as feeder fish. These are fishes that are specifically bred as food and can be cheap.

The problem however is that you don’t know the environment in which those fishes were bred. Feeder fish bred in poor conditions can bring parasites and diseases to your fish. If you still want to use feeder fish, it is recommended that you place them in quarantine for about a week before placing them in the tank.

2 – Herbivores

Herbivore fish are those that eat algae, seaweeds, herbs, and vegetables. Examples are: African cichlids, pacus, plecos, and silver dollars

Regarding herbs, available research data is all about using mint as a dietary supplement, not as the regular feed. I have an anecdotal story from my friend who feeds his fish small amounts of basil, thyme, parsley, and oregano. However, he doesn’t believe in feeding mint to his fish. I guess I will have to show him what the research says on this topic.

There is however plenty of information about feeding fruits and vegetables to fish. Many people who have pet fishes say that they feed melons, apples, bananas, grapes, mango, papaya which they serve raw and cut into small pieces.

There are also aquarium fish enthusiasts that feed their fish assorted vegetables such as: lettuce leaf, zucchini, spinach, pumpkin, carrots, and cucumber, mostly one at a time. Always peel hard rind vegetables and remove the stems from spinach.

It is also highly beneficial that you feed this type of fish algae as it is their natural food. If you don’t know where to buy algae you can encourage its growth at home with stuff you already have at home.

Encouraging Fresh Algae Growth

Get a glass container and a rock from your aquarium. Place the rock in the container and place this container at your windowsill under direct sunlight. Once your rock has a good amount of algal growth, give it back to your fish.

3 – Omnivores

A majority of aquarium fish eat both meat and plant-based food. Examples of this type of fish are: goldfish, mollies, discus, and catfish.

To give these fish a balanced diet, feed them twice a day, one commercial fish food (either in pellets or flakes) in the morning, and plant-based food in the afternoon. This will help keep your fish at optimum health and maintain their beautiful color.

How Much To Feed Your Fish?

It depends on what type of fish you have. Aquarists however recommend that you shouldn’t give your fish more than what they can eat for 5 minutes. If there are leftovers, start adjusting the amount until you hit the optimum. Also, always remove leftovers within 24 hours before they can start decaying in the tank.

Changing Fish Food

When you change your fish’s food it can sometimes take time for them to get used to it. If it bothers you that much, you can mix fish attractants with your fish food. Here one fish food and supplements that some many fish owners found found u:

Homemade Fish Food Recipes

I have 2 recipes to share for some of you who like to prepare homemade fish food to either save on cost or perhaps you’d like to know what goes into your pet’s food.

Easiest High Protein Fish Food

Here’s a very simple and low-budget fish food that your meat-eating fish will love.

Ingredients and equipment:

  • 5 pcs hard-boiled eggs
  • Strainer
  • Wide saucepan

The procedure:

1. Peel eggs and carefully separate the yolks from the egg whites. Then squeeze the egg yolks through the strainer.

2. Scatter evenly around the pan while passing egg yolk through the strainer or use a fork to do that. Try not to touch the egg yolks to preserve their texture.

3. Dry the egg yolks. There are 2 ways to do that:

  • Sun-drying: This takes a few hours and can introduce contaminants if left uncovered.
  • Oven: Fast and perfect for cloudy days or if you don’t have a place where there is direct sunlight.

4. If using the oven method, use a low heat setting. Stir the egg yolk every minute to prevent burning.

5. Your fish food will be ready when the texture looks and feels like pellets and the color is golden yellow.

Recommendations:

  • Feed fish 2 times a day with this food on warm days and once during cold days.
  • Store in an air-tight jar to avoid moisture.
Cheap & Easy Homemade Fish Food | High Protein

Broccoli Fish Food

This simple fish food is perfect for your herbivore fishes.

Ingredients and equipment:

  • 1 pc broccoli floret
  • Water
  • Saucepan

Method:

1. Boil water in a saucepan. Add broccoli and simmer for 5-8 minutes or until soft. Let cool.

2. Break it apart and proceed to feed your fish.

Feeding Broccoli to Goldfish

Notes:

  • Always soften any vegetables you want to feed your fish by steaming or blanching. This will help the food sink to the bottom.
  • You can replace broccoli with other vegetables that can be steamed i.e. carrots.
  • Clean aquarium regularly.

Takeaways

  1. Fish can benefit from placing mint in an aquarium when it gets coated with micro amounts of the mint’s essential oil by making the fish resistant to helminth parasites.
  2. When using herbs for the aquarium, take care that only the roots are submerged because the essential oils are at the highest amount in the leaves and stems.
  3. Mint shouldn’t be fed to fish in large amounts as its taste can be strong for fish.

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Sources

“Will Plants in an Aquarium Raise the Nitrite Level?” by Robert Boumis in The Nest

“How To Improve Fish Tank Health With Aquaponics Systems And Herbal Gardens” by Tom Duncan in Permaculture Research Institute

“Feeding Your Fish” by n.a. in Bob’s Tropical Fish

“EFFECT OF MINT (MENTHA ARVENSIS) LEAF SUPPLIMENTED DIET ON HEMATOLOGICAL CHANGES IN COMMON CARP CYPRINUS CARPIO Vol 7 Issue 4” by Dr. N. R. Jaiswal in JETIR (ISSN-2349-5162)

“Use of Clove, Mint and Camphor Essential Oils on Confinement of Clown Anemonefish Amphiprion ocellaris (Cuvier 1830): Anesthetic Effects and Influence on Water Quality” by Antonio Ostrensky et al in Journal of Aquaculture

“Growth promoter effect of peppermint (Mentha piperita) on rohu (Labeo rohita)” by Dharmakar Padala et al in International Journal of Fisheries and Aquatic Studies

“Difference between Peppermint Oil and Peppermint Extract” by Editorial Staff in Difference

Andrea

A young Italian guy with a passion for growing edible herbs. After moving to the UK 6 years ago in a tiny flat, it was impossible to grow herbs outside. So I start my journey in growing indoor and so I decided to share my knowledge.

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