Need ah, you know in the water under the condition of direct current, the positive pole of oxygen, the negative pole for hydrogen. And they are stable in the ratio of oxygen 1: hydrogen 2. But before this their ratio is not 1: 2. So the fish life in the water is the need for oxygen, however, some fish need less oxygen, some fish need more oxygen, fish in the natural environment is generally in certain circumstances it is to find a bit of time to rise out of the water to look for the lack of oxygen, including fish in the deep sea. In the home of the feng shui fish, generally need to use electricity to bar the water to do certain out!