54 MARCH 2025 • WORLD AQUACULTURE • WWW.WAS.ORG hideout tank, the color tends to fade gradually. Research suggests that the presence of live plants in aquaria can enhance the coloration of fish, including N. nandus, due to various physiological and behavioral mechanisms. Many studies have documented the phenomenon of enhanced coloration in fish reared in planted tanks compared to those in bare tanks (Bartoszek et al. 2018; Dalton et al. 2020). The enriched environment provided by live plants offers numerous advantages, such as reduced stress levels, increased natural behavior expression, and improved water quality, all of which contribute to vibrant coloration in fish. One possible explanation for the enhanced coloration observed in planted tanks is the psychological well-being of the fish. Fish reared in enriched environments with live plants exhibit lower stress levels and higher activity levels, which may positively impact pigmentation processes (Maas et al. 2019). Reduced stress allows fish to allocate more energy towards pigmentation production, resulting in brighter and more vibrant colors. Body Shape and Fins. N. nandus fish exhibits an elongate, flat body resembling a leaf-like structure, adorned with various fins. Particularly distinctive is its elongated dorsal fin, extending along the back and contributing to a profile akin to a leaf. Observations revealed that in a planted tank, the shape of the body and fins remained pronounced and erect, whereas in a plain glass tank, the fins appeared flaccid, and the coloration appeared dull. (Figure 4). Feed acceptance. N. nandus are carnivorous in their natural environment, primarily feeding on small aquatic insects and invertebrates. They are column feeders and as a result of their natural hunting behavior feeding prepared feeds under captivity was a big challenge. However, acceptance of a variety of live and frozen foods, such as brine shrimp, small fish, and tubifex has been observed in captive culture of N. nandus. In our study, tubifex was fed to the fishes twice a day. Enhanced feed acceptance of N. nandus in a planted tank compared to a plain glass tank was observed, and may be attributed to several factors related to the enriched environment provided by live plants. Live plants offer opportunities for natural behaviors such as foraging and exploration, which can stimulate appetite and increase feeding activity (Steenbergen et al. 2021). Planted tanks may host microorganisms and small invertebrates associated with live plants, providing additional food sources for fish. This dietary diversity can enhance feed acceptance and nutritional intake (Bidwell et al. 2018). Challenges in maintenance under tank culture. The proliferation of filamentous algae in planted aquaria is a frequent concern, influenced by various factors such as lighting, nutrient levels, and water circulation. To mitigate the growth of filamentous algae, it is essential to maintain a stable and balanced environment while simultaneously promoting the growth of desired plants and inhibiting algae overgrowth. Regular monitoring is conducted, and if filamentous algae growth is detected, manual removal is performed to prevent hindrance to the free movement of fishes within the tank (Figure 5). Managing diseases in N. nandus presents a major challenge related to its high sensitivity. Infestations of parasites and bacteria are common issues that can lead to various diseases in this species. Skin, fin, or gill inflammation, as well as damage caused by external parasites, are among the common problems encountered during culture (Figure 6), especially in tanks with hideouts. The occurrence of disease in N. nandus may be observed to be more prevalent in plain glass tanks compared to planted tanks because of several factors related to the environmental conditions and stress levels experienced by the fish. Planted tanks often exhibit better water quality because of the presence of live plants, which can help in nutrient uptake and oxygenation (Bidwell et al. 2018). Improved water quality reduces the likelihood of opportunistic pathogens thriving and causing diseases. Conclusion In conclusion, the culture of N. nandus within a planted habitat can notably enhance the visual appeal of these leaf-like fish. One potential benefit of rearing N. nandus in planted tanks over plain tanks is enhanced coloration. For species such as N. nandus an enriched environment provided by live plants offers advantages in terms of water quality, habitat complexity, behavioral stimulation and dietary diversity, all of which contribute to accelerated growth and improved health. This discussion emphasizes the benefits of culturing N. nandus in planted tanks; further research could offer valuable guidance for refining fish care methods and enhancing production. FIGURE 5. (A) Filamentous algae growth in planted tank, (B) Manual removal of filamentous algae from the tank. FIGURE 6. Nandus nandus affected by pathogens resulting in (A) Gill rot, (B) Fin rot.
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