Performance of Co-Housed Neon Tetras (Paracheirodon innesi) and Glowlight Rasboras (Trigonostigma hengeli) Fed Commercial Flakes and Lyophilized Natural Food.

Robert Kasprzak,Aleksandra Górecka,Anna Beata Grzeszkiewicz

doi:10.3390/ani11123520

Robert Kasprzak, Aleksandra Górecka + Show 1 more

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https://doi.org/10.3390/ani11123520

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Abstract

Simple SummaryThe ornamental fish trade is a growing, developing global industry. However, on a scientific level, most aspects of aquarium fish nutrition remain to be a totally uncharted territory, awaiting to be explored. Thus, a feeding trial was conducted to compare the long-term effects of commercial flake feeds and dietary supplementation with natural food on the condition of neon tetras and glowlight rasboras, a setup which exemplified ordinary household community tanks. Even though there were no differences in growth between experimental groups, laboratory analyses revealed that the used feeding strategies had different outcomes in each species. Particularly, natural food appeared to cause a pathological lipid accumulation in the livers of rasboras, while no such effect was found in the tetras. The study highlights the need to conduct more in-depth feeding studies on ornamental fish, with special attention paid to their taxonomic origin and diversity.Little to no research has been conducted thus far regarding aquarium fish nutrition. In order to ensure the welfare of house-kept ornamentals, such studies should take into account that there are distinct biological differences occurring between different fish species/taxa, especially in regard to the structure of their digestive organs. Accordingly, a 12-week trial was executed to assess the effects of two commercial flakes and a mix of lyophilized natural food on the condition of co-reared neon tetras, Paracheirodon innesi (Characidae), and glowlight rasboras, Trigonostigma hengeli (Danionidae). The four feeding groups were as follows: (T)—Tetra flakes; (O)—Omega flakes; (TO)—Tetra + Omega; (TOL)—Tetra + Omega + Lyophilizate (twice a week). There were no differences in final body weight (FBW) between the feeding groups of either species, but in the case of neon tetras, FBW increased significantly from the initial value only for the T group. However, histological observations and measurements of digestive organs (livers, intestines) showed pronounced differences between the two species. The supplementation with natural food in group TOL caused lipoid hepatic degeneration only in the rasboras. The healthiest histological structure of livers and longest intestinal folds were found in group T of the tetras and group TO of the rasboras. Whole-mount staining for bone and cartilage did not reveal any significant deformities or differences in terms of bone mineralization. In conclusion, it was outlined that concurrent feeding of co-housed, anatomically diverse ornamental fish species is a highly ambiguous task, because the nutritional strategy applied for a community tank may yield radically divergent effects, most of which may remain unnoticed when depending only on external body observations and measurements. Most emphatically, this was highlighted in regard to the dietary supplementation with natural food—although no significant effects were observed in neon tetras, severe lipoid liver degeneration occurred in glowlight rasboras.

Highlights

The ornamental fish trade is a vast market of near-global range which generates an estimated yearly income surpassing tens of billions euro, with freshwater species accounting for more than 90% of the trade [1,2]
Anecdotal observations made by hobbyists and fish producers indicate that both species are relatively mild-tempered, seldomly proceeding with actions such as fin-nipping; they can be safely stocked in community tanks with other small ornamentals
As we have shown in our previous nutritional experimentation on juvenile crucian carp, Carassius carassius [82,90], similar growth rates do not always give the whole picture of the condition of aquarium-reared fish, in regard to the structure of digestive organs or the skeleton

Summary

Introduction

The ornamental fish trade is a vast market of near-global range which generates an estimated yearly income surpassing tens of billions euro, with freshwater species accounting for more than 90% of the trade [1,2]. These numbers obviously pale in comparison with the sizes of both the aquaculture production and capture fisheries [3], but it is a distinct and noteworthy industry . Means to improve natural food, which is crucially important during early weaning, are being studied profoundly [14]

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