## 3 Results and Discussion
### Reduction Rate of Phosphate  
In wastewater, phosphates are transformed into orthophosphate and are available for plant uptake as a source of nutrients; however, this may cause a nutrient imbalance and an imbalance in the material cycling processes of the natural phosphorus cycle in the ecosystem [37]. Controlling excessive phosphorus content in wastewater is a key factor in deterring the eutrophication of surface water. Its excessive presence may cause losses of livestock and introduce potentially lethal algal toxins into drinking water, which are very bad for aquaculture industries and humans alike [38].  
_E. crassipes_ is the best plant among the five species to treat phosphate in aquaculture wastewater, as shown in Figure 4. Since organic phosphate acts as a nutrient for plants, _E. crassipes_ was highly efficient in absorbing phosphate for its nutritional needs, with a reduction rate almost reaching 100% and a total of 0.34 mg/L phosphate reduced after 14 days of phytoremediation treatment. This species has long fibrous roots capable of providing extensive surface area for the plant to carry out physical, chemical and microbial processes for nutrient absorption and nitrification processes [18]. In addition, [39] reported _E. crassipes_ reduced 50.04% of phosphate from an aquarium with a population of _Sarotherodon melanotheron_ (blackchin tilapia) within 12 days of treatment.  
Figure 3: Reduction rate of NH\({}_{3}\)-N using five plant species after 14 days of phytoremediation.  
Based on the graph of the phosphate concentrations, _I. aquatic_ was very inconsistent and removed the least amount of the pollutant. However, the concentration of phosphate decreased at days 4, 6, and 12. _S. molesta_ had the most consistent phosphate removal rate, but the readings reached a maximum removal concentration on the 10 th day and stayed constant until day 14. The concentration of phosphate at the end of the experiment in the control tank was the highest compared to tanks with plants, because phosphate is essential for plants' life-sustaining reactions, which include energy transfer, protein activations, and regulation of metabolic processes [40, 41]. That could explain the difference between the control tank with no plants for absorption, and the tanks with five macrophytes species.  
An independent t-test analysis showed no significant value (\(p<0.05\)) between the phosphate reductions by all five species after 14 days, except for _E. crassipes_ and _I. aquatic_, since the highest average removal value was 0.34 mg/L by _E. crassipes_, with I. _aquatica_ being the lowest--0.17 mg/L. The efficient reduction of phosphate from the wastewater comes from plant uptake and the presence of diverse substrates [42]. This pollutant is the major constituent in adenosine diphosphate (ADP) and adenosine triphosphate (ATP), which acts as a building block for nucleic acids, sugar phosphates, nucleotides, and many more, especially during the active growth of plants. Phosphates are crucial for energy storage and transfer in photosynthesis and respiration, essential for normal growth, maturity, and root system development, but too much phosphate in a plant's system may be lethal [40, 41, 42, 43]. In addition, some macrophytes need phosphate more than other macrophytes, depending on the plants' type, requirements and its surrounding environment.  
The results found in the present study were in line with other previous studies [9, 44, 45, 46, 47, 48]. A similar pattern of results was obtained to indicate the ability of phytoremediation in removing different pollutants. Phytoremediation for treating wastewater remains popular until now due to it being cost-effective, environmentally friendly, and sustainable with low maintenance.