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Abstract. Water quality is one of the factors that strongly affect the cultured fish. Aquaculture practices in coal mining void often face mass death of their cultured fish due to water quality deterioration. The use of aquatic plants is aimed to improve the water quality of the fish cage in coal mining void and especially to improve the organic matter. Water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiote) and water fern (Salvinia molesta) were applied into the fish cages in coal mining void. The water quality from each cage was examined every day for a two weeks period, to identify the pattern. The results showed that the plants are potential agents for improving the water quality and the organic matter in the fish cages in post coal mining void.
Key Words: Eichhornia crassipes, Pistia stratiote, Salvinia molesta, phytoremediation, water quality.
Introduction. Aquaculture practice using floating cage in post-coal mining voids in East Kalimantan is still increasing nowadays. Half of the supply of carps and tilapias in East Kalimantan come from the voids. However, an interesting phenomenon occurs in the cultivation area, namely the sudden mass death of the cultivated fish that usually occurs 2-3 times a year. A study conducted by Pagoray et al (2013) detected a significant decrease of water quality in the void during the mass death of the fish. Depletion of pH, DO, and increased concentrations of toxic compounds, such as NH3, H2S and NO3, were pointed as the cause of the mass deaths. Besides being characterized by a low pH, acid mine water also contain metals with high concentrations, so that it can adversely affect the health of the environment and humans (Juari 2006). There are some methods which can be applied to eliminate the water quality problem. One of them is the bioremediation method using aquatic plant (phytoremediation).
Phytoremediation is a bioremediation process using certain plants in order to eliminate or remove the contaminants from soil and water. Besides, plants can also be used as an oxygen supplier as well as for absorbing excessive organic and inorganic matters in the water (Xiang et al 2009). Some invasive plants are well known for their high potential of nutrient removal (Lu et al 2010) and hyper accumulators (Wickramasinghe & Jayawardane 2015)....