Scientists tested whether special plant-based oils could help young tilapia fish grow better and stay healthier. They added different amounts of herbal oils—made from plants like oregano and thyme—to fish food over 10 weeks. Fish that ate the right amount of these oils grew faster, had better digestion, and showed signs of stronger immune systems. This research suggests that using natural plant oils instead of artificial additives could be a better way to raise fish for food while keeping them healthy.

The Quick Take

  • What they studied: Whether adding herbal essential oils (natural plant extracts) to fish food would help young tilapia grow faster and stay healthier
  • Who participated: Young tilapia fish (fingerlings) divided into five groups that received different amounts of herbal oil supplements over 72 days, with a control group receiving no supplements
  • Key finding: Fish that received moderate amounts of herbal oils (30-60 mL per kilogram of food) grew significantly faster, converted food to body weight more efficiently, and showed improved immune system markers compared to fish receiving no supplements
  • What it means for you: If you eat farmed tilapia, this research suggests that fish farmers may soon be able to raise healthier fish using natural plant-based additives instead of synthetic chemicals, potentially improving both fish welfare and food quality

The Research Details

Researchers conducted a controlled experiment where they raised young tilapia fish in separate tanks and fed them different diets. One group (the control) received regular fish food with no additives. The other four groups received the same food but with increasing amounts of herbal essential oils mixed in—similar to how you might add vitamins to your diet. The researchers carefully measured how much the fish grew, tested their blood, examined their intestines under a microscope, and even looked at which genes were turned on or off in their bodies. This type of study is called a “dose-response” experiment because it tests different amounts (doses) of a treatment to find the best level.

The herbal oil blend contained eight different plant compounds: carvacrol and thymol (from thyme), oregano oil, 1,8-cineole (from eucalyptus), alpha and beta pinene (from pine), and limonene (from citrus). These are all natural compounds that plants make to protect themselves. The researchers chose these specific oils because previous studies suggested they might have health benefits for animals.

This research matters because fish farming is a major source of food worldwide, but it currently relies on synthetic additives to keep fish healthy and growing well. Finding natural alternatives could make fish farming more sustainable and environmentally friendly. Additionally, understanding how natural compounds affect fish health helps us learn more about how these same compounds might work in other animals and potentially in humans.

This study was published in a peer-reviewed scientific journal (Frontiers in Veterinary Science), meaning other experts reviewed it before publication. The researchers used a controlled experimental design with multiple treatment groups and a control group, which is a strong research approach. They measured multiple outcomes (growth, blood markers, intestinal health, and gene expression) rather than just one thing, which gives a more complete picture. However, the study was conducted only on fish in laboratory conditions, so results might differ in real-world fish farms with different water conditions or fish populations.

What the Results Show

The most important finding was that fish receiving 30-60 mL of herbal oils per kilogram of food showed the best results. These fish grew significantly heavier than the control group, gained weight faster, and converted their food into body weight more efficiently—meaning they needed less food to gain the same amount of weight. This is important for fish farming because it means farmers could produce more fish with less food, saving money and resources.

The researchers also found that these herbal oils improved the fish’s intestinal health. When they looked at the intestines under a microscope, they saw that the finger-like structures (called villi) that absorb nutrients were taller and had more surface area in fish that received the oils. This explains why these fish grew better—they were absorbing nutrients more effectively from their food.

Blood tests showed that fish receiving the herbal oils had stronger immune systems. Their blood contained more white blood cells and higher levels of protective proteins called antibodies. The fish also showed better antioxidant status, meaning their bodies were better protected against cellular damage from normal metabolism.

The study found that genes related to intestinal barrier function (ZO-1 and occludin) were more active in fish receiving the herbal oils, suggesting their intestines were better protected against harmful bacteria. Additionally, a stress-response gene called HSP70 was less active in these fish, indicating they experienced less physiological stress. Interestingly, the highest dose of herbal oils (240 mL/kg) did not perform as well as the moderate doses, suggesting there is an optimal amount—too much is not better than the right amount.

This research builds on earlier studies showing that herbal essential oils have health benefits for various animals. Previous research had suggested these oils could improve growth and immunity, but this study is one of the first to comprehensively examine how they affect multiple aspects of fish health simultaneously, including gene expression. The findings align with what scientists know about how these plant compounds work—they have antimicrobial and antioxidant properties that help protect cells from damage.

The study was conducted in controlled laboratory conditions with young fish, so results might differ in larger commercial fish farms where conditions are less controlled. The researchers did not specify the exact number of fish used in each group, making it harder to assess statistical power. The study only looked at one species of fish (Nile tilapia), so these results may not apply to other fish species used in aquaculture. Additionally, the study did not examine the cost-effectiveness of using these herbal oils compared to other additives, which would be important for practical application in fish farming.

The Bottom Line

Based on this research, fish farmers may consider supplementing tilapia feed with 30-60 mL of herbal essential oils per kilogram of food as a natural alternative to synthetic additives. This recommendation has moderate confidence because the study showed clear benefits in controlled conditions, but more research in real-world farm settings would strengthen this recommendation. Farmers should start with the lower dose (30 mL/kg) and monitor fish health and growth before increasing amounts.

Fish farmers and aquaculture companies should care most about these findings, as they could improve their operations. Consumers who prefer sustainably-raised fish with fewer synthetic additives may also find this relevant. People with fish allergies or sensitivities should not assume this changes anything about fish safety. This research is not directly applicable to human nutrition, though it may eventually inform similar research in other animals.

In the study, improvements in growth were visible within the 72-day trial period, with the most significant differences appearing after several weeks of consistent supplementation. If fish farmers implement these findings, they could expect to see improved growth rates and feed efficiency within 4-8 weeks of starting supplementation.

Want to Apply This Research?

  • If you’re a fish farmer or aquaculture enthusiast using an app, track weekly measurements of fish weight, feed consumption, and feed conversion ratio (weight gained per amount of food eaten) when implementing herbal oil supplements. Compare these metrics to your baseline data from before supplementation.
  • If you manage a fish farm, the practical change would be to gradually introduce herbal essential oil supplements to your feed at the recommended 30-60 mL/kg rate, while maintaining detailed records of fish health indicators, growth rates, and costs to determine if the benefits justify the expense in your specific operation.
  • Monitor fish health monthly by observing activity levels, appetite, and appearance. Track growth metrics (weight and length) every 2-4 weeks. Test water quality parameters regularly to ensure the herbal oils don’t affect tank conditions. Keep records comparing your results to your previous baseline data and to industry standards for your fish species and farm size.

This research describes results from a controlled laboratory study on fish and should not be interpreted as medical advice for humans. While herbal essential oils have been used traditionally, they are not regulated as medicines in most countries. If you are considering using herbal essential oils for any health purpose, consult with a qualified healthcare provider first. This study was conducted on fish in controlled conditions and results may not apply to other species or real-world farm settings. Always follow local regulations regarding feed additives in aquaculture. The findings are promising but represent early-stage research; more studies are needed before widespread commercial implementation.