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Biofloc technology (BFT) systems have been driven towards increased sustainability in the last decade. BFT depends on maintenance of the optimal carbon-to-nitrogen (C/N) ratio through supplementation with organic carbon sources. The types of carbon sources and addition strategies are critical considerations in BFT systems. Thus for the purpose of this review, a thorough search of the literature was conducted to gather relevant information from reliable sources, ranging from reputable journals to books and useful reports in the field of BFT. Keywords used for the literature search include: 'biofloc technology systems', 'carbon sources', 'solid carbon sources', 'effects of carbons sources', 'carbon source addition strategies', 'nutritional quality of bioflocs', 'carbon sources and water quality', 'C/N ratio in BFT', and 'carbon sources and bacterial community'. Among the several peer-reviewed articles, books and technical reports consulted, 147 (dated from 1987 to 2020) were relevant for the preparation of this review. The current review thus examines the subject of supplemental carbon sources in BFT systems and discusses the various effects of their application with respect to the culture organism, microorganisms, water quality and the nutritional quality of flocs. The benefits and challenges associated with the types of carbon sources used in BFTs are also presented. Suggested organic carbon sources and their addition strategies are provided, and further research directions are proposed.

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Tilapias are a prominent aquaculture fish species, placing second only to carps in terms of the world's fish production (FAO, 2018).According to FAO (2018), their production is predicted to increase from 58% in 2016 to about 62% in 2030, and is expected to surpass that of carp by the year 2025 (Ahmadi et al., 2016). This is because of their resilience to varied stress conditions and their characteristic fast growth rate, which make them a preferred aquaculture species in most places of the world, including Central America, Asia and Africa (Nitzan et al., 2017).Many species of tilapia are broadly euryhaline (Chervinski, 1961), while other species exhibit preference for fresh or lower salinity waters. The ability of these organisms to acclimate to various salinity conditions results in some corresponding changes in their osmoregulatory processes in order to ensure that maintenance of the internal

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Fish preservation methods including use of formalin and freezing are widely used to preserve fish specimen in the laboratory to maintain their freshness for future laboratory analysis. This present study aimed to investigate the effects of fixation and freezing on the morphometric characteristics of Nile tilapia, Oreochromis niloticus. Forty (40) samples of a single cohort of O. niloticus were obtained from the Tono reservoir in Navrongo, Ghana. Total length (TL) and body weight (W) of each fish were measured. Twenty (20) samples of O. niloticus were subjected to freezing at -4ºC whilst the remaining twenty (20) were fixed in 4% formaldehyde solution. The study lasted for thirteen (13) days during which the length and weight were determined repeatedly in a sequence during the storage period. Although there was no significant difference (p > 0.05) in the change of length and weight measured during the study, all samples showed some degree of shrinkage within the storage period. For samples preserved by freezing, there was a 5.62 % and 19.61 % reduction in length and weight respectively, while those preserved in formalin reduced by 5.24% and 10.72% in length and weight respectively. For condition factor (k), there was no change at the end of the experiment for samples preserved by freezing but a marginal increase of 0.08% was realized for those preserved in formalin. Though shrinkage occurred in both samples preserved in formalin and freezing, the greatest shrinkage was recorded by those preserved by freezing.

The study on the evaluation of a high speed tagging device for Oreochromis niloticus (Nile tilapia) stock assessment was conducted in the Vunania dam in the Kasena-Nankana District of the Upper East Region of Ghana for two months(April-May 2014). A total of 49 Nile tilapia fishes were obtained during the period of study. Out of this number 28 were males and 21 were females representing 57.1% and 42.9% respectively. In the research the females Oreochromis niloticus had a range of 11 cm to 20 cm total length with a standard deviation of 2.0998 and a weight range of 25 g to 140 g with a standard deviation of 28.7697. Males had a range of 11.30 cm to 16.8 cm with a standard deviation 1.4409 and a total weight range of 27 g to 110 g with a standard deviation of 18.4637. In totality the sampled Oreochromis niloticus had a minimum weight of 25 g and maximum of 140 g and a mean of 82.5, minimum length of 11 cm and a maximum of 20 cm and a mean of 15.5. MS222 at a dose of 0.3 g/l [23] was used for the sedation with a minimum sedation time of 12 sec and maximum time of 238 sec and a mean of 125, minimum recovery time of 27 sec and a maximum of 311 sec and a mean of 169, a minimum tagging time of 4sec and a maximum of 122 sec and mean of 63.