How Often to Change the Water for Fish in an Aquarium, Why Fish Cannot Leave Water, How Long They Can Survive Out of Water, and Which Fish Can Survive Out of Water

Nowadays many people like to keep fish at home. When keeping fish, besides feeding them regularly, you also need to change the water regularly. So, how often should you change the water for fish in an aquarium? Why can't fish leave water? If there is no water, how long can they live? Which fish can survive out of water?

1. How often should you change the water for fish in an aquarium?

Generally speaking, when the weather is relatively cold in winter, the water in the tank will not need to be changed so quickly, so it does not need to be changed as often as in summer. When we notice that the fish begin to float to the surface and gulp air with their mouths wide open, it means the fish in the aquarium are already short of oxygen, and that is when we need to change the water. We can also grow some beneficial aquatic plants in the aquarium, as they can replenish oxygen in the water through photosynthesis. In addition, when changing in new water, pay attention to the temperature difference of the water; the temperature difference must not be too large, otherwise the fish will be very uncomfortable and become ill.

2. Why can't fish leave water?

Fish rely on the four gills in the gill cavity to take in oxygen from the water, and then expel carbon dioxide from their bodies into the water through the opening and closing of the gill covers. Once they leave the water, water cannot flow into the gill cavity, the gills will quickly dry out, and the gill filaments will stick to each other. As a result, the fish can no longer breathe with their gills, and without breathing, the fish die from lack of oxygen.

3. If there is no water, how long can they live?

How long a fish can live without water depends on the species. Carp can live 10-20 minutes out of water, crucian carp can live 20-40 minutes out of water, and other fish can live 1-10 minutes. But some fish can live for several days as long as there is a certain amount of moisture. The snakehead has relatively strong vitality; as long as there is a layer of water at the bottom of the container, in a cooler place, it is no problem for it to live for a day. If the environment is very dry and it is exposed to the sun, it will probably last only about half an hour. After leaving the water, koi can survive for about 10 minutes or even 1 hour without dying; this has a lot to do with whether there is water on its body and the size of the fish. If a koi under 10 cm is placed directly on dry ground, after 10 minutes it is basically beyond saving. If a large koi weighing more than ten jin is placed in a moist, shady environment, it may live for an hour.

4. Which fish can survive out of water?

1. Mudskipper: Mudskippers live in swamps and estuaries as well as on mudflats. They are famous for being able to climb and hop out of water, can breathe air outside water and the water vapor in the gill cavity, and can survive on land for long periods. If they do not regularly come out of the water, they will die. Mudskippers have the habit of leaving the water to feed. Whenever the tide goes out, they often rely on the muscular stalks of their pectoral fins to crawl and jump on the mudflats to feed, or climb onto rocks and mangroves to prey on insects, or climb onto stones to sunbathe. After it leaves the water, its well-developed gill chambers are filled with air, and it dips its tail in the water as an auxiliary means of breathing. Living out of water has become an important habit for it.

2. Climbing perch: The climbing perch is commonly known as the walking fish. It is famous for being able to live, crawl, and climb out of water. It can breathe air and lives in ponds and ditches. Sometimes it uses the hard spines on the lower edge of its tail and gill covers to make sudden jumps, and can briefly leave the water or “walk”, hence the common name walking fish. The climbing perch has a very well-developed labyrinth organ and can breathe air. It supports its body with its pectoral fins and swings its tail fin left and right, moving forward like a seal, and can maintain life on land for several hours. This is because part of the gills is in the shape of rose-petal-like folds, densely covered with capillaries, which can directly absorb oxygen from the air and release carbon dioxide from the blood.

3. Eel: Eels can breathe through their skin. Sometimes when they leave the water, as long as their skin remains moist, they will not die.

4. Snakehead: The snakehead can still survive for quite a long time after leaving the water.

5. Killifish: A kind of fish that can survive in trees for months, also called the mangrove killifish. This fish lives in Latin American swamps. Whenever the swamps where they live dry up, they strive to “climb” into the trees in the swamp and hide in cracks or hollows of branches or trunks, living for several months. This small creature can temporarily change its physiological structure so that it can breathe air, use its gills to retain moisture and nutrients, and use its skin to excrete waste. After returning to the watery homeland, it will return to its original form.

6. Lungfish: Lungfish use plump sac-like structures as lungs. When the river water dries up in the dry season, they hide in the substrate and wrap themselves in a waterproof dried mucus cocoon to help them survive. The “lung” is in fact derived from a specialized, well-developed swim bladder, so some species can survive by breathing air even without water. In water, the fins can support the body like legs.

However, it is worth noting that all fish need water. Even if they can live out of water, it is only temporary. Water fish and crocodiles also cannot live on land for long periods.