## 1 Introduction  
Aquaculture is the breeding, rearing, and harvesting of aquatic life, such as fish, shellfish, prawns, algae, and other organisms living in an aquatic ecosystem. Aquaculture is one of the fastest-growing economies in the world food economy. Global aquaculture production has doubled in the past decade in terms of value and volume, and now supplies one-third of the seafood consumed worldwide [1]. Asia dominates this production, accounting for 88.91% by volume in 2014 [2]. There is no doubt that the contribution of aquaculture to the food supply will increase in the future due to the growing world population.  
However, unsustainable aquaculture can give rise to new problems, such as water pollution, if the effluent and wastewater are not meticulously maintained. Water pollution caused by effluent from ponds is one of the main issues related to aquaculture [3,4]. Aquaculture has become large enough to have significant impacts on the environment, and some environmental concerns have been expressed by environmental activists and scientists [5]. In most freshwater aquaculture ponds, wastewater is generated before harvesting the stock, in which all of the particles and nutrients are present. Potential pollutants come from fertilizers, food spills, and the waste of reared animals. Some of the major sources of wastewater pollution are residual food waste, feces, metabolic by-products, and residual biocides and biostats [6]. These products contain organic carbon, nitrogen, ammonia, urea, bicarbonate, phosphate, vitamins, and therapeutics, which, in high concentrations, are harmful to the aquatic ecosystem and eventually disrupt the natural food chain [7; 8]. According to [PERSON] et al. [9], wastewater containing these substances will have major negative effects on human health as well as the environment. This will cause major disturbance to our ecosystem balance eventually, making the Millennium Development Goals (MDGs) hard to achieve [9; 10].  
There are a lot of conventional methods that help to remove pollutants from the aquatic environment such as adsorption, biological treatments, disinfection, ultraviolet irradiation, and advanced treatment technologies like advanced oxidation processes (AOPs). Although these methods can significantly improve the removal of pollutants, the capital, operational, and maintenance costs for these treatments are high, especially for advanced treatments [11; 12]. Phytoremediation, however, is one of the environmentally friendly and low-cost methods of removing pollutants from water and soil. This treatment is a remediation method that uses various plants to reduce, extract, and hold excessive nutrients and pollutants from a contaminated medium [13]. Phytoremediation methods can be categorized based on how the pollutants are removed from the environment, such as through degradation, extraction, containment or a combination of two or more techniques. Plant species considered to be ideal phytoremediation agents have a high biomass, a good root system, and are fast-growing and easy to grow [14; 15].  
Therefore, this study aims to determine the efficiency of five different plant species--_Centella asatica, Ipomoea aquatica, Salvinia molesta, Eichhornia crassipes_, and _Pistia stratiotes_--in removing pollutants from catfish aquaculture wastewater. These five plants are believed to have a high potential for reducing pollutants from wastewater. Plant selection in phytoremediation treatment is crucial, as the plant is the main tool in removing the pollutants [16].