, the more water in the fish tank, the better, because the greater the amount of water, the better to maintain the water quality, which is more helpful to the health of the fish, so full is better than half. But a higher water level will also increase the water pressure at the bottom, and the oxygen content at the bottom will decrease, so it's better for small fish to have a lower water level, so that the fish will not have a sense of urgency, and will breathe more smoothly.

2. What are the requirements

for fish tank water? 1. Water temperature: The first thing to pay attention to in fish tank water is the water temperature. The temperature changes too much, which is very harmful to the health of fish. Usually, it is better to keep the water temperature at about 20 C. Not only can tropical fish survive at this temperature, but also the growth of eurythermic fish will become rapid at this temperature.

2. Water quality: The quality of fish tank water is also very important. Poor water quality can cause various diseases. Usually, in order to maintain water quality, water needs to be changed regularly, usually once a week. In addition, if you don't want to change water frequently, you'd better install a filter in the fish tank, which can also play a role in maintaining water quality.

3. Depth of water: Generally, the fish tank cannot be filled with water. If there is too much water, the water pressure at the bottom will be higher and the dissolved oxygen will be lower, so the fish at the bottom cannot be kept alive. Usually the water surface should be about 5 centimeters from the top of the fish tank, and if it is some small fish, the water level can be further down.