Bio-nanotechnology employing bio-sourced nanomaterial is an emerging avenue serving the field of fish medicine. Marine-sourced chitosan nanoparticles (CSNPs) is a well-known antimicrobial and immunomodulatory reagent with low or no harm side effects on fish or their human consumers. In this study, in vitro skin mucus and serum antibacterial activity assays along with intestinal histology, histochemical, and gene expression analyses were performed to evaluate the impact of dietary CSNPs (5 g kg⁻¹ dry feed) on rainbow trout resistance against ‘enteric redmouth’ disease. Two treatment conditions were included; short-term prophylactic-regimen for 21 days before the bacterial challenge, and long-term therapeutic-regimen for 21 days before the challenge and extended for 28 days after the challenge. Our results revealed higher antibacterial defense ability and positive intestinal histochemical and molecular traits of rainbow trout after dietary CSNPs. The prophylactic-regimen improved trout health while the therapeutic regimen improved their disease resistance and lowered their morbidity. Therefore, it is anticipated that CSNPs is an effective antibacterial and immunomodulatory fish feed supplement against the infectious threats. However, the CSNPs seem to be more effective in the therapeutic application rather than being used for short-term prophylactic applications.

Aquaponics is an eco-friendly system that integrates soilless cultivation and aquaculture. This study aimed to assess the water quality, hematological and biochemical parameters, and growth performances of tilapia (Oreochromis niloticus), as well as Lettuce (Lactuca sativa) yield, reared for 110 days in a newly developed deepwater culture (DWC), as a prototype built in the Upper Egypt Center of Development owned by the Academy of Scientific Research and Technology (ASRT) in Sohag Governorate, Egypt. The experimental work consisted of two DWC systems. Fish (n= 300 with an average weight (18 ± 0.8 g)) were fed daily for five days a week with 2% of the total biomass with a protein feed content (30%). The results showed that water quality parameters were within the optimal range for tilapia culture except for pH. The hematological and biochemical parameters and growth performances were within typical values. The growth and yield of Lettuce were measured through fresh weight, and they were better than in other studies. Aquaponics technology can be used to produce high-quality tilapia and lettuce.

For the sake of sustainability and ecosystem preservation, it is crucial to look for alternate protein sources for aquatic organisms fed in captivity. In the current study, many biomarkers were used to evaluate the potential applications for earthworms (Eisenia foetida) in aquaponic systems as alternative fishmeal for feeding tilapia (Oreochromis niloticus). A four-month feeding experiment using Nile tilapia (O. niloticus) was conducted to determine the impact of substituting 25% of the fish meal in the feed formula with earthworms (Eisenia foetida). Growth performance, food consumption, haematological parameters, biochemical parameters, and histochemical invistigation as well as growth hormone gene expression values have been evaluated in O. niloticus. Our data indicated that final weight, weight gain, feed conversion ratio (FCR) and feed efficiency ratio (FER), in addition to haematological parameters and biochemical parameters, showed non-significant differences between fish fed a normal diet and fish consumed an earthworm diet under aquaponic systems. In contrast, fish get a regular diet; the gut and liver of tilapia fed an earthworm diet showed a normal histological structure, no indication of any particular pathology, and a normal amount of protein and carbohydrates. Growth hormone level expression in muscle of fish fed earthworm was similar to fish fed a normal diet. To summarise, the partial incorporation of earthworm meals in the diets of O. niloticus has a substantial and favourable influence on Tilapia's health status, implying that earthworm meal is appropriate as an animal protein source in the diet of Tilapia in an aquaponics system.