~ 2662 ~ Journal of Entomology and Zoology Studies 2017; 5(6): 2662-2664 E-ISSN: 2320-7078 P-ISSN: 2349-6800 www.entomoljournal.com JEZS 2017; 5(6): 2662-2664 © 2017 JEZS Received: 18-09-2017 Accepted: 23-10-2017 Kouberi Nath Division of Fisheries, ICAR-RC for NEH Region, Umiam, Meghalaya, India Sanjay Kumar Das Division of Fisheries, ICAR-RC for NEH Region, Umiam, Meghalaya, India Corresponding Author: Kouberi Nath Division of Fisheries, ICAR-RC for NEH Region, Umiam, Meghalaya, India Water quality and growth of Cyprinus carpio at different stocking density in bio FLoC and non- bio FLoC system Kouberi Nath and Sanjay Kumar Das DOI: https://doi.org/10.22271/j.ento.2017.v5.i6aj.9085 Abstract A 60 days indoor trial was conducted at ICAR-RC for north eastern hill region, Umiam in glass aquaria (30L) without soil base. The performance of three stocking density @ 2.0 nos/m 2 , 4.0 nos/m 2 , 6.0 nos/m 2 with BFT and non BFT has been investigated using sweet potato powder as carbohydrate source. The water quality and growth performance of common carp (Cyprinus carpio) was access at different stocking density in bioFLoC and non biobloc system. The feeding rate was maintained @ 2% of body weight. The results show a significant difference (p<0.05) in total suspended solids (TSS), and FLoC volume among the treatments. The TSS, FLoC volume and total heterotrophic bacterial count (THB) was higher in 6 nos/m 2 in BFT system. The biological oxygen demand (BOD) load and Aeromonas count was found highest in non BFT system at 6 nos/m 2 . The transparency and water exchange rate were lowest at 6 nos/m 2 stocking density in BFT system. The total ammonical nitrogen and phosphorus load also differs significantly in BFT and non BFT system at different stocking density. The survival was observed highest for 2 nos/m 2 in BFT system and lowest in 6 nos/m 2 in non BFT system. The daily growth rate (DWG) was not differing statistically among the treatments. The present study suggests that adding sweet potato as carbohydrate can increase the carrying capacity of culture system. Addition of sweet potato also reduce water demand by 20% at high stocking density culture. Keywords: Bio FLoC, sweet potato, stocking density, water exchange, ammonical nitrogen Introduction The increasing world population demand for more protein rich food across the globe. To increase the productivity intensive aquaculture with more feeding and high stocking density practiced to increase the productivity of water bodies. High stocking density and excessive feeding affects aquaculture industry negatively by accumulating residual feed, metabolites, toxic substances [4] . As a result, the disease emerges and reduce productivity due to mortalities. Bio FLoC technology is a system in which heterotrophic bacteria convert fish waste into microbial biomass (bio FLoC). BFT improving the water quality in the culture environment and subsequently reduces water use. It is a system that promotes continuous recycling and reuse of nutrients [5] . The bio FLoC technology continues to increase in the aquaculture industry worldwide for super intensive aquaculture system to reduce water consumption and increase fish production per unit. Aquaculturists shows their interest on bio FLoC which utilizes pond microbial community to improve water quality and maximize feed recycling by maintaining a high carbon/nitrogen (C: N) ratio in the water [3] . Bio FLoC stimulates heterotrophic bacterial biomass and reduce ammonical nitrogen load by utilizing nitrogenous waste [9] . In bio FLoC system, the total suspended solids of 200-300 mg/L and 100-300mg/L respectively for tilapia and shrimp are maintained. The total turbidity of 75-150 NTU is normally recommended for well-maintained bio FLoC system the solids are controlled with a clarifier at a flow rate of for every 3-4 days, in a settling tank [7] . Various fish species are cultured in a bio FLoC system like tilapia, catfish, shrimp prawn which can tolerate and survive in adverse environmental conditions. Different stocking density has different effects on water quality, growth performance and water re-use [7] . The study related to the effects of different stocking density are limited in bio FLoC system [10] . A few studies have been conducted using various stocking density to know the effects for tilapia,