World Aquaculture Magazine -December 2021

66 DECEMBER 2021 • WORLD AQUACULTURE • WWW.WA S .ORG One important characteristic of tubifex worms is cyst formation when exposed to dry conditions. This occurs in natural habitats such as a reservoirs and ponds that are exposed to water level fluctuations and periodic dessication. The survival time of encysted worms during drying was about 14 days but may survive for as long as 70 days when moistened with water periodically (Kaster and Bushnell 1981). GrowthMedia Different combinations of media can be used (Table 1). Growth media such as cowdung, mustard oil cake, vegetable waste, deoiled rice bran can be used. Media should be adequately mixed with water and kept for fermentation and decomposition of organic matter. After fermentation, water flow through culture media should be maintained for 24 h. The supplementation of culture tanks with media is done every seven days. A fermented media mixture of 50 g/L of quail manure, 100 g/L stale bread, and 50 g/L tofu waste has been used to produce tubifex worms with 66 percent protein and 13 percent fat (Herawati et al . 2016). Worm grazing and filtration by tubifex results in an increased sludge reduction rate, removal of the protein fraction of sludge and TABLE 1. Tank culture media and production capacity. Comb i na t i on o f c u l t ur e me d i a Pr odu c t i on Bread – 20% 666 mg/cm 2 in 15 d Wheat bran – 20% Cowdung – 20% Soil – 40% Wheat bran – 35% 419 mg/cm 2 in 60 d Cow dung – 25% Mustard oil cake – 20% Fine sand – 20% Soybean meal – 30% 659±17 mg/cm 2 in 60 d Mustard oil cake – 20% Wheat bran – 20% Cowdung – 20% Sand – 10% Powdered mustard oil cake. Dried cow dung. targets the aerobic degradable fraction of activated sludge (de Valk et al . 2017). Amixture of 40 percent mustard oil cake, 30 percent soybean meal and 30 percent mud wetted in cattle blood medium can be used as substrate for the commercial culture of tubificid worms, which produces a yield of 684 ± 4 mg/cm 2 (Hasan et al . 2019). Culture Methods TankCulture System A cement tank of 4.5 m × 1.5 m × 1 m can be used as a container for tubifex culture, and continuous water flow should be maintained (Marian and Pandian 1984). As tubifex are photophobic, the culture system should be kept in a shaded area. Depurated tubifex inoculums should be used for the culture. Depuration and disinfection of tubifex can be done soon after collection, ensuring that the inoculum is free from pathogens and contaminants, followed by washing to remove disinfectant. Tubifex can be inoculated to the tank in the early morning or late evening. The biomass would be at a peak after fifteen days and then gradually decrease. Harvesting can be done every few days to maintain the biomass.