Iron-containing substances are known to affect the growth of many aquatic plants, such as Egeria densa. However, the concentration of these substances on the growth of E. densa was unknown to our best knowledge. We designed and performed an experiment to explore the effect of different iron concentration levels on E. densa. We observed that iron does play an important role in the overall growth of E. densa. We also found that there is a relationship between the amount of iron introduced and the growth achieved. The data indicates that (1) both plants in the iron solutions had more growth than the plant in the control tank (0.0% iron); (2) the plant submerged in the iron solution of 0.1% had a growth rate higher than the plant submersed in the 0.19% solution by a factor of two, approximately. We conclude that a ~0.1% iron solution is the optimal solution for the fast growth of E. densa.