Studies On Symbiosis Ecosystem Of Fish And Grass

Grass planted in symbiosis ecosystem of fish and grass could absorb the nutrition of the waste water which supplied a feasible condition of normal growth, and was the food of the fish, so it was an important meaning.To evaluate the effect of biofiltration provided by terraneous on a closed system of recirculating water, adaptive comparisons were made on effluent irrigated Lolium multiform Lam. planted in the models of tray, float and soil soilless cultures. Comparison between the three culture models, tray hydroponic culture showed the best adaptability due to low content of free radical, MDA and free proline, good growth condition and high N and P absorbed by the plant followed by floating soilless and the soil cultures.To estimate the effect of bio-filtration of terrestrial pasture Lolium multiform Lam. on a recirculating aquaculture system with a low cost and simple construct, tray and floating soilless cultures were made by means of artificial substratum. It was showed that plant height and biomass rised parabolicly in the two culture models of Lolium multiform Lam., and the total nitrogen and phosphorus decreased exponentially in the aquacultural wastewater. The other parameters of water quality were improved in various degrees. The growth rates and purification efficiency of the tray soilless culture were obviously better than those of the floating soilless culture. Symbiosis system made up of tray soilless culture of Lolium multiform Lam. and tilapia would be a great development foreground.Tray soilless culture evolved by the nutrient flow technology in which there was only a layer of nutrient liquid and the oxygen was very enough was designed to improve the effect of wastewater purified by the terraneous. It was showed that when the height of the tray was 1 cm, and six layers of clothes were laid on the tank to filtrate and hold wetness the wastewater, furthermore, the gradient of the tank was between 2 and 8, the tray soilless culture was the most feasible.There were a great deal of kinds of the grass with high quality and quantity fed to fish. To determine the best symbiosis ecosystem of fish and grass on a closed system circulated yearly, several cold and warm grass was selected to analyse the adaptability and nutrition absorbed. Itindicted that Lolium multiform Lam. and lemarthria compressa were the best option due to high adaptability of wetness, high coarse protein, fat and fibre and so on in the leaf, high biomass, high bio-filtration effect of N and P, adaption to the low or high temperature, resist to the plant diseases and insect pests, and the food of fish whose forage was grass.Research on the symbiosis ecosystem of Lolium multiform Lam. and tilapia showed that the largest load was 2159.66g m"3, and the best quality offish and grass was 0.222. The ecosystem would destroy when the load was more.