The goal of this study was to identify and estimate the abundance of microorganisms associated to biofloc culture system, developed from a `macrocosm-microcosm' system type. In first section (cylinder 1000 L), 75 juveniles tilapias were inoculated with 5.0 ± 0.95 cm mean length and 4.2 ± 1.08 g mean weight were placed. Daily, the fishes were fed with commercial diet, maintaining a C/N = 15:1 ratio, carbon (molasses and rice dust) and nitrogen (from commercial feed) supply was controlled. This culture condition was maintained during 14 weeks. Several microorganisms associated to the flocs were identified using conventional microbiological tests. To estimate the abundance of organisms associated to flocs, a stereoscopic and optical microscopes were used. Both microscopes were connected to an interphase program for images counting (Image ProPlus v.7.0). The results shown changes in abundance of different microorganisms communities associated to flocs during 14 weeks of experiment. The main groups found in flocs were: bacteria, algae, ciliates, rotifers and nematodes. The results confirm that the bioflocs contributes significantly as in situ natural food source, because a great number of organisms may be associated to them including heterotrophic microbial communities like genus Sphingomonas, Pseudomonas, Bacillus, Nitrospira, Nitrobacter and yeast Rhodotorula sp. The literature show that these microorganisms favoring water quality and physiological good health at organisms in culture.

For the management of Spodoptera frugiperda, botanical extracts have been used to reduce the environmental impacts of synthetic chemical pesticides. In the present investigation, the insecticidal activity of the acetonic and methanolic extracts of Heterotheca inuloides (Asteraceae) and of the main compound 7-hydroxy-3,4-dihydrocadalene on this pest as well as its ecotoxicological effect on Poecilia reticulata were evaluated. A greater insecticidal response was obtained from the acetonic extracts than from the methanolic extracts, with LC₅₀ values of 730.4 ppm and 711.7 ppm for samples 1 and 2, respectively. Similarly, there was a lethal effect on 50% of the P. reticulata population at low concentrations in the acetonic extract compared to the methanolic extract. The sesquiterpene 7-hydroxy-3,4-dihydrocadalene has greater insecticidal activity by presenting an LC₅₀ of 44.36 ppm; however, it is classified as moderately toxic for guppy fish.

This study aimed to evaluate the development and the increase in the skin pigmentation of the organism Heros severus cultured in a biofloc system with diets enriched with carotenoid pigments. The culture was made in 80 L water tanks with 20 juvenile organisms of H. severus; each treatment was made by duplicate. Four experimental diets were used: a) trout feed, El Pedregal®; b) TetraColor®; c) carrot and d) beetroot. The diet that obtained the highest values regarding the growth of the fish was the control diet. Regarding the coloration of the fish, the beetroot diet was the diet that presented the highest values with 9.55 μg of total carotenoids in tissue, presenting significant differences (P = 0.001) concerning the other diets, proving that a diet based on beetroot can be a good option for the culture of ornamental fish. Because it allows the organisms to have a survival rate above 90%, have similar growth to the control group, and a significant improvement in coloration, being a natural carotenoid low-cost source to improve the commercialization of organisms. Nevertheless, it did not present significant differences (P = 0.005) regarding beetroot and TetraColor® diets, while it presented significant differences with the carrot diet.

Biofloc technology (BFT) has recently attracted great attention due to minimal water exchange and reduced feed intake. This study aimed to recognize daily changes in the digestive physiology of Oreochromis niloticus between a traditional system and BFT. The enzyme activity of trypsin (try), chymotrypsin (chy), leucine aminopeptidase (lap), alkaline proteases (alk), lipase (lip), and amylase (amy), along with the gene expression of trypsin ( try ), chymotrypsin ( chy ), pepsin ( pep ), amylase ( amy ), and phospholipase ( pla ) were measured throughout a daily cycle. Samples were taken every 4 h in a 24 h cycle under a 12:12 L:D photoperiod. During 60 days, fish were feed three times a day (zeitgeber time, ZT: 0, 4, and 8) with a fishmeal‐based diet containing 32% of crude protein and 5% of lipid, where molasses was added as a carbon source in BFT. No significant differences were found in fish performance among treatments at the end of the experiment. The activity of all tested enzymes significantly ( p < 0.05) increases during the dark period in both treatments, where the same activity pattern was found in try and lip. The maximum expression levels of digestive gene enzymes between treatments show a marked effect dependent on the presence of light and dark phases. The cosinor analysis showed an activity in try, lap, and lip with a significant rhythmicity ( p < 0.05). Our results demonstrate that some processes related to the digestive physiology of tilapia that respond directly to daily rhythmicity are modified under the constant presence of feed in BFT. These findings should be considered when establishing new optimized culture protocols.

The effect of live yeast Rhodoturula glutinis was evaluated on juvenile Oreochromis niloticus cultivated in a Biofloc system. Growth performance and the expression of innate response and relevant oxidative stress genes were evaluated after a 12-week feeding trial. Three experimental treatments were evaluated in a conventional tilapia culture (control), Biofloc culture (BFT), and Biofloc with the addition of the live yeast R. glutinis 1×106 CFU g-1 (BFT+Rg), with four replicates per treatment. In all cases, commercial food was supplied to the organisms (32% protein and 5% lipids). O. niloticus juveniles (7.02 ± 0.04 g) were randomly distributed in 12 tanks, each with 15 animals. BFT+Rg treatment showed a significant increase in weight gain compared with the other treatments. Significant improvements were found in Fulton's condition factor, feed conversion rate, and hepatosomatic index under Biofloc conditions, BFT, and BFT+Rg treatments. No significant differences were observed in survival. R. glutinis directly influenced gene expression in the liver and intestine. The expression of tnfa, tgfb, hsp70, and gpx, genes in the liver significantly increased in the BFT+Rg treatment compared with the other treatments. Similarly, a significant increase was found in intestinal il1b, tnfa, tgfb, trf, hsp70 gpx, and cat expression patterns in the BFT+Rg treatment. Based on the performance and immune response, the present study suggests the use of R. glutinis as a strategy to increase the productivity of tilapia in Biofloc culture.