 Dear students, in today's experiment, I will demonstrate you how we can measure the dissolved oxygen concentration by using dissolved oxygen meter. We will also check the effect of temperature on dissolved oxygen consumption. The dissolved oxygen concentration is the most important environmental factor in fish culture. In the broadest sense, the dissolved oxygen concentration is no more important than any other environmental factor because any factor which is outside the range tolerated by fish in intensive fish culture may cause stroke or even death. So what makes the dissolved oxygen concentration so important in fish culture is the speed with which it changes. It can change from optimum to lethal in the matter of hours or even minutes. There are different methods to measure dissolved oxygen concentration. The selection of methods based on the number of ponds or tanks to be used, second the accuracy which we required and third the cost of the measuring technique. Now let's start the procedure. Dear students, to perform this experiment, we need dissolved oxygen meter. Dissolved oxygen meter has two components, a sensor which is also called as probe and a meter. The sensor react with oxygen and produce an electrical signal in proportion to oxygen concentration. This electrical signal is then amplified and translated into concentration unit which is displayed by meter. Dissolved oxygen meter do not measure oxygen directly but it may at the voltage produced by chemical reaction of oxygen with the different components of sensor. The second material which we require is beaker which contain point water. Accurate measurement of deoconcentration with polygraphic sensor requires moving the sensor in the water. Oxygen is consumed across the membrane so failure to move the sensor will create an oxygen depleted microphone around the sensor tip and show a measurement that is too low. Move the sensor up and down or side to side about one foot per second to prevent this problem. Dear students, now we will check the effect of temperature on the dissolved oxygen consumption. For this we need dissolved oxygen meter and two beakers containing point water. The first beaker contains cold water and the second one contains warm water. Place fishes in both beaker. Now let the fishes settle, take a stopwatch and take reading at different time intervals. Now I will take the reading of dissolved oxygen consumption in the first beaker containing cold water for 10 seconds. Dear students, now you can check the reading of dissolved oxygen consumption in cold water. Now I will take the reading of dissolved oxygen consumption in second beaker containing warm water for 10 seconds. Dear students, now you can check the difference of dissolved oxygen consumption in both beakers containing cold and hot water and you can clearly observe that the dissolved oxygen consumption in the beaker containing warm water decreases. Dear students, now you check the difference of dissolved oxygen consumption in both beakers containing cold and hot water. Now we will take reading of dissolved oxygen consumption after 5 minutes. Now dear students, we will take the readings again after 5 minutes. So first of all I will take reading in cold water, after this I will take reading in warm water. Dear students, now you have observed the difference of dissolved oxygen consumption in both beakers containing cold and hot water. You clearly observed that dissolved oxygen consumption in beaker containing warm water is gradually decreasing. The reason behind is that when temperature increases, gas and water molecule gain more energy which in turn breaks the weak interaction of oxygen and water molecule which causing the oxygen to escape. Dear students, this experiment helps us to access the water quality. It also signifies the importance of dissolved oxygen concentration for the survival of fish and aquatic organisms.