PRIYADARSHANA, R.W.H.H.2021-03-292021-03-292013UWU/AQT/09/0033http://www.erepo.lib.uwu.ac.lk/bitstream/handle/123456789/6274/UWULD%20AQT%2009%200033-08052019105541.pdf?sequence=1&isAllowed=yOrnamental fish industry plays a considerable role in the economy of Sri Lanka since the globalization ornamental fish industry. Maintenance of aquariums with ornamental fish has become a hobby of people and aquarium owners but the controlling excessive algal bloom has become a hindrance. Excessive algal growth is a nuisance for aquarists, due to decreasing dissolved oxygen level, absorbing the nutrients. It is also hazardous to fish and plants. Present study attempts to develop a method to control excessive green algal blooms in aquariums combining the effects of Copper Sulfate and aquatic plant Valisnaeria. Complete randomized design was used under laboratory condition. Thirty six tanks were used for the experiment and seventy two Betta Splendens fishes were used. five treatments (concentrations) for Copper Sulfate, Valisneria spiralis plants and controls for both treatments were used in triplicate. This survey was done using ANOVA and Minitab 14 software. Results indicate that both the Copper Sulfate and the Valisneria plants are effective in controlling algae under aquarium condition. Tukey's pairwise comparison has shown that all the treatments with Copper sulfate were significantly different from the control (P<0.05). The highest algal decline level was shown in 0.5 ppm significant level. And also it can be concluded that biomass of 7.12 g /in 6 1 of water is adequate for controlling algae in a volume of 230 1 water containing 0.12,Ing/1 Chlorophyll a. Key words, Aquariums, Chlorophyll, Copper Sulfate, Green algae, Valisncria biomassenAquatic Resources Technology Degree Programme ( AQT)Thesis