The study is particularly relevant as the global ornamental fish market increasingly seeks environmentally friendly alternatives to synthetic color enhancers. Color intensity is one of the most important factors determining the commercial value of ornamental fish, especially koi betta fish, whose vibrant patterns attract hobbyists and breeders alike. At the same time, red dragon fruit peel is commonly discarded as agricultural waste despite containing valuable natural pigments and antioxidants. The research demonstrates that this underutilized by-product can be transformed into a functional ingredient for aquaculture feed while supporting more sustainable agricultural practices.
Agricultural Waste with High Nutritional Value
Red dragon fruit peel contains betacyanin, the pigment responsible for its characteristic red color, along with β-carotene, vitamin C, flavonoids, polyphenols, and antioxidant compounds. These substances are known to contribute to pigmentation and may also support fish health.
Unlike mammals, ornamental fish cannot synthesize carotenoids naturally. Instead, they must obtain these pigments through their diet. Once absorbed, carotenoids accumulate in specialized pigment cells beneath the skin, resulting in brighter and more vivid body coloration. Because of this biological limitation, nutrition plays a central role in maintaining the appearance and market value of ornamental fish.
According to the authors, utilizing dragon fruit peel as a feed ingredient also addresses two challenges simultaneously: reducing agricultural waste and replacing synthetic pigments with a natural alternative.
How the Research Was Conducted
The researchers evaluated the effectiveness of dragon fruit peel flour by raising 12 koi betta fish for 45 days under controlled conditions.
The fish were divided into four dietary treatments:
- 10% red dragon fruit peel flour added to feed
- 20% red dragon fruit peel flour
- 30% red dragon fruit peel flour
- 0% dragon fruit peel flour (control group)
Each treatment consisted of three fish maintained individually in separate containers. Researchers observed changes in body coloration on Day 0, Day 15, Day 30, and Day 45, while water temperature, pH, and fish survival were monitored throughout the experiment to ensure that the feed additive remained safe.
Natural Pigments Produced Brighter Fish
The study found that adding dragon fruit peel flour consistently improved the brightness of koi betta fish, although the degree of improvement depended on the dosage.
Key findings include:
- Fish receiving 20% dragon fruit peel flour exhibited the greatest improvement in color intensity.
- The 30% treatment also produced substantial color enhancement.
- The 10% treatment improved coloration but more gradually.
- Fish in the control group showed little noticeable color improvement.
- Color changes became visible as early as Day 15 in the 20% and 30% treatments, while the 10% treatment showed clearer improvement around Day 30.
The researchers noted that although increasing carotenoid levels generally improves pigmentation, fish can absorb only a limited amount of these compounds. Excessive supplementation may reduce absorption efficiency, explaining why the 20% concentration produced the best overall result despite the higher pigment content in the 30% treatment.
No Negative Impact on Fish Survival
Beyond color enhancement, the feed additive proved safe throughout the study.
All koi betta fish survived the entire 45-day maintenance period, resulting in a 100% survival rate across all treatment groups. This suggests that incorporating dragon fruit peel flour into feed does not negatively affect fish health under the tested conditions.
The authors attribute this outcome partly to the peel's antioxidant content, including polyphenols, flavonoids, and vitamin C, which may contribute to physiological stability and disease resistance during cultivation.
Sustainable Benefits for Aquaculture
The findings have practical implications for ornamental fish farmers, feed manufacturers, and agricultural producers.
For fish breeders, dragon fruit peel flour offers a relatively inexpensive natural pigment source capable of improving product quality and market value. Feed manufacturers may consider incorporating agricultural by-products into commercial formulations, reducing dependence on synthetic additives. Meanwhile, fruit processors and farmers could create additional economic value from what is currently considered waste.
The research also supports broader sustainability goals by promoting circular resource use, where agricultural residues are converted into high-value aquaculture products rather than discarded.
As ethically summarized from the authors' discussion, Darna Susantie of Politeknik Negeri Nusa Utara and Muhammad Fiqih Zulendra of BPPP Bitung conclude that dietary supplementation with 20–30% red dragon fruit peel flour effectively enhances koi betta coloration, with the 20% concentration providing the most efficient pigment absorption while maintaining excellent fish survival.
The researchers recommend that future studies investigate additional dosage levels and evaluate herbal feed formulations to further optimize natural pigmentation strategies in ornamental aquaculture.
Author Profile
Darna Susantie is a researcher and lecturer in the Department of Fishery and Maritime Technology, Politeknik Negeri Nusa Utara, Tahuna, Sangihe Islands Regency, North Sulawesi, Indonesia. Her research focuses on aquaculture, ornamental fish nutrition, fish feed development, and sustainable fisheries. This study was conducted in collaboration with Muhammad Fiqih Zulendra from BPPP Bitung, whose work also contributes to fisheries development and aquaculture innovation in Indonesia.
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