Scientists tested whether adding lemongrass and chamomile oils to fish food could help European seabass (a type of fish raised in farms) handle stress better and grow stronger. The fish that ate food with these plant oils grew faster, ate more, and had healthier bodies than fish eating regular food. The oils also seemed to reduce harmful bacteria in the fish’s guts and skin. The fish showed no signs of getting sick from the oils, and their stress levels stayed normal even when they were handled for measurements. These results suggest that plant-based oils could be a natural way to improve fish health and happiness in aquaculture farms.

The Quick Take

  • What they studied: Whether adding lemongrass or chamomile essential oils to fish food would help farmed seabass grow better, handle stress, and stay healthier
  • Who participated: European seabass fish that were about 520 days old and weighed around 156 grams at the start of the study. The exact number of fish wasn’t specified in the abstract
  • Key finding: Fish eating food with lemongrass oil grew significantly faster and ate more food than fish on regular diets. Both oils reduced harmful bacteria in the fish’s digestive system and skin, with chamomile being especially effective. The fish stayed healthy and showed no signs of sickness from the oils
  • What it means for you: If you eat farmed seabass, this research suggests that fish farmers may soon be able to raise healthier fish using natural plant oils instead of medications. This could mean safer, better-quality fish at your grocery store. However, this is early research, and more testing is needed before farms widely adopt this practice

The Research Details

Researchers divided farmed seabass into groups and fed some groups food mixed with lemongrass oil, some with chamomile oil, and some with regular food (the control group). They fed the fish this way for about a month while measuring how much they ate, how fast they grew, and how healthy they looked. To test whether the oils helped with stress, the scientists deliberately stressed the fish twice during the study by handling them for 15 minutes—something that normally happens on real fish farms when workers measure and check the fish.

The scientists measured many things to understand if the oils were working: how much the fish weighed, how much they ate, the size of their organs, their blood health, stress chemicals in their blood (like cortisol), and the amount of bacteria living in their guts and on their skin. They took measurements at different times throughout the study to see if the effects got stronger or weaker over time.

This research approach is important because it tests something practical that fish farmers actually do—add things to fish food to improve health. By measuring both growth and stress responses, the scientists could see if the oils helped fish handle the tough conditions of farm life. Testing the fish during stressful situations (like handling) made the study more realistic, since real farms do handle fish regularly

This is described as a ‘preliminary study,’ which means it’s early-stage research that shows promise but needs more testing. The study was published in a scientific journal focused on fish health, which is a good sign. The researchers measured many different health markers, which gives a fuller picture than just looking at one thing. However, the abstract doesn’t specify exactly how many fish were studied, which makes it harder to judge how reliable the results are. The fact that fish responded differently to the oils suggests the results might vary in real farm conditions

What the Results Show

Fish that ate food with lemongrass oil showed the strongest improvements. They ate more food each day and gained weight faster than fish on regular diets. The lemongrass group’s growth kept improving throughout the month-long study. Fish on both oil-enriched diets (lemongrass and chamomile) showed better overall body condition and more efficient use of their food—meaning they gained more weight from the same amount of food.

The oils also improved the fish’s blood health. Fish eating the oil-enriched food had higher total protein levels and better blood cell counts. These improvements stayed consistent throughout the study and weren’t affected by the stress tests, suggesting the oils made the fish genuinely healthier, not just temporarily boosted.

One of the most interesting findings was the reduction in harmful bacteria. Fish eating chamomile-enriched food showed the biggest decrease in bad bacteria living in their guts and on their skin after just one month. This is important because bacteria infections are a major problem in fish farms. The oils appeared to work like a natural antibiotic or immune booster.

The fish’s organs showed positive changes too. Their livers became healthier (measured by hepatosomatic index), and they had less fat stored in their belly area. Stress chemicals in the blood (cortisol, lactate, and glucose) stayed within normal healthy ranges for all groups, even after the handling stress tests. This suggests the oils didn’t just mask stress—they helped the fish handle it naturally. However, individual fish within the same feeding group responded differently, meaning some fish benefited more than others from the oils

This research builds on earlier studies showing that plant essential oils can help reduce stress and boost immunity in various animals. The findings align with what scientists know about lemongrass and chamomile having calming and antibacterial properties. However, this appears to be one of the first studies testing these specific oils in seabass at these doses, so it’s filling a gap in knowledge about how to naturally improve fish farm health

The study is labeled ‘preliminary,’ meaning it’s early research that needs confirmation. The abstract doesn’t specify the exact number of fish studied, which makes it hard to judge how confident we should be in the results. The study only lasted about a month, so we don’t know if the benefits continue longer or if fish eventually get used to the oils. The research was done in controlled lab conditions, which may not perfectly match real fish farms with thousands of fish. Finally, individual fish responded differently to the oils, suggesting results might vary depending on the fish’s genetics or other farm conditions

The Bottom Line

Based on this preliminary research, lemongrass and chamomile essential oils show promise as natural additives for farmed fish food (confidence level: moderate, since this is early-stage research). The evidence suggests they could improve fish growth, health, and stress resistance. However, fish farmers should wait for larger, longer studies before making major changes to their feeding practices. If farms do try these oils, they should start with small amounts and monitor results carefully

Fish farmers and aquaculture companies should pay attention to this research as a potential way to improve fish health naturally. Consumers who care about how farmed fish are raised might be interested, as healthier, less-stressed fish could mean better quality seafood. People concerned about antibiotic use in farming should note this as a potential alternative. However, people with lemongrass or chamomile allergies should be aware these oils are being tested in food production. This research is too early to recommend that individual fish tank owners try these oils at home

In this study, positive changes started appearing within the first two weeks and continued improving through the month-long feeding trial. If farms adopted this practice, they’d likely see benefits within 2-4 weeks of adding the oils to fish food. However, the long-term effects beyond one month are unknown, so farms would need to monitor fish health continuously

Want to Apply This Research?

  • If you’re tracking seafood quality or sustainability, note the farm source and whether they use natural additives like essential oils. You could rate your seafood purchases based on farming practices that prioritize fish welfare
  • When buying farmed seabass or other fish, look for labels indicating natural or welfare-focused farming practices. Ask your fishmonger or check online whether local farms use natural health supplements. Consider supporting farms that invest in fish health through natural methods rather than relying solely on medications
  • Track your seafood purchases and note which farms or brands use natural additives. Over time, you can observe if fish from these sources tastes better or seems fresher. Share feedback with retailers about your preference for naturally-raised fish to encourage more farms to adopt these practices

This research is preliminary and has not yet been confirmed by larger studies. The findings apply to farmed seabass and may not apply to other fish species or to wild fish. This information is for educational purposes and should not be used to make medical decisions about seafood consumption. People with allergies to lemongrass or chamomile should be aware these oils are being tested in fish farming. Consult with a healthcare provider or registered dietitian if you have specific health concerns about farmed fish. Fish farmers should consult with aquaculture specialists before implementing new feeding practices based on this research.