Rawapening Lake is one of Indonesia's national priority lakes that is experiencing environmental problems which are urgently required to be solved due to its functions. The decline in the environmental quality of Rawapening Lake includes sedimentation, water pollution and excess of nutrients, especially Phosphorus (P) and Nitrogen (N) into the lake that induced uncontrolled growth of aquatic plants, one of which is water hyacinth (Eichhornia crassipes (Mart.) Solms). Many activities had been done to reduce the covering of water hyacinth in Rawapening Lake that tends to increase by the time, but no significant result has been achieved. Therefore, this research was conducted in order to study the growth rate of water hyacinth with mesocosm in Rawapening Lake as a baseline to develop suitable management. There were three different sites, namely: Site I in the floating net cage area (FNCA), Rowoboni Village, Site II in the natural area of Bejalen Village which is far from the aquaculture sites, and Site III in the upper reaches of the Tuntang river, Asinan Village. The research was performed in November -December 2019 with the measurements of growth rate, addition number clump and water hyacinth covering every week. The experiment was conducted in the 1 x 1 meter mesocosm, with three replication in every site. In every mesocosm water hyacinth with similar initial weight of 160 grams and number of leaves 6-7 strands were grown in the mesocosm. On day 7 (H7) the average wet weight of water hyacinth increased by 201%. In the fourth week (H28) the average wet weight of water hyacinth increased by 788% compared to the initial weight when planted. The highest relative growth rate (RGR) value of water hyacinth was at site III (7.26%/ day), followed by Site I (7.03%/day), and Site II (6.40%/day), respectively. The doubling time (DT) value of water hyacinth at the site I was 9.9 day, site II -10.8 day, and site III -9.6 day. One clump of water hyacinth weighing 160 grams was able to cover 1 m 2 of mesocosm within 21 days. On the basis of these results, to manage water hyacinth blooms one has to consider its growth rate.

Feed is a major factor in determining the success of aquaculture business. The quality and quantity of feeding properly will maximize the growth of fish. Various research and application of technology has been made to obtain alternative feed source so as to reduce the level of dependence on the food production industry. The eutrophication condition of Rawapening Lake has triggered the water hyacinth (Eichhornia crassipes (Mart.) Solms) to grow out of control. It speeds up the loss of water weeds, cover the surface of the water into the fishing area and degrade water quality. The purpose of this study was to determine the potential of water hyacinth as an alternative fish feed ingredient. In addition, it is also an effort to control the growth of water hyacinth in Rawapening Lake. The descriptive analysis method with a quantitative approach was chosen in this study. After making flour, water hyacinth has a protein content of 12.51%. Water hyacinth fine flour mixed with other ingredients including fish meal and fish feed bisamenghasilkan rice bran protein content of 30.2477%. The results of testing the stability of feed in water (Water Stability Feed) showed that the feed was destroyed after being immersed in cold water for 17 hours. The buoyancy test shows the feed is classified as a submerged type. The feed sinks because it has a specific gravity which is greater than the specific gravity of water. The feed hardness test shows that the feed is not destroyed after being given a load of 500 grams. The heavier the load that the feed can hold, it means the feed is getting harder. Protein content of 30.2477% indicates that alternative fish feed has competitive quality because it is able to meet the protein needs of cultivated fish. Especially fish cultivated in tropical areas which have lower protein requirements (20-30%).

Rawapening is one of Indonesia's national priority lakes, which is experiencing environmental damage and urgently needs rehabilitation. The decline in water quality is caused by sedimentation and organic and inorganic waste that triggers eutrophication. Rehabilitation of Lake Rawapening is important to improve the health of freshwater resources. The ecological engineering approach is the most appropriate choice to rehabilitate these water conditions. The character of the macrophyte is the key factor for successful rehabilitation. Three macrophytes, Hydrilla verticillata (L. f.) Royle, Eichhornia crassipes (Mart.) Solms and Salvinia molesta D.Mitch., charactierized. Their characteristics, including growth rate, salt tolerance, dissolved oxygen production and consumption, nutritive value, and preferred food by herbivore fish were evaluated. The results indicated that H. verticillata has the highest growth rate, is the most tolerant to salinity change, produces more oxygen, has the highest nutritive value, and is the most preferred food for herbivore fish. H. verticilata is recommended as the best candidate to be used as a forcing function to drive the Rawapening lake into more economic and environmentally valuable for a resident. As the other two species also have high nutritive value, they can be recommended as a source of feed for animals as well. For better management, these two macrophytes required more often regular removal. Other economic and environmental values can also be achieved from E. crassipes and S. molesta.

High sedimentation and the entry of organik and inorganik pollutants, especially P and N, have led to the eutrophication of Rawapening Lake waters. These conditions triggered an uncontrolled booming of water hyacinth aquatic weed (Eichhornia crassipes (Mart.) Solms). The presence of water hyacinth triggers a significant loss of water compared to local weeds through evapotranspiration. The invasion of water hyacinth causes various problems, including depletion of water oxygen content which has an impact on decreasing fish production, damaging natural beauty, and also affecting public health. Many efforts to control water hyacinth in Rawapening Lake have been carried out both physically and by utilizing biological agents. One of the efforts to control the density of water hyacinth in Rawapening Lake is to use it as compost raw material. Water hyacinth contains various elements that are useful for making quality compost, including calcium (Ca), sodium (Na), potassium (K), iron (Fe), copper (Cu), and others. Water hyacinth root contains sulfates and phosphates, the leaves contain carotin and the flowers contain delphinidin-3-diglucosida. The various nutrients contained in water hyacinth make quality compost capable of meeting the nutritional needs of cultivated plants. This article aims to review the use of water hyacinth as a basic material for making compost which is useful for fertilizing agricultural cultivation activities