It’s less about how much water they’re in and more about how much oxygen and waste is in that water.
Assuming it’s a fish that can breath without moving, just like a person sealed in a box eventually the fish will run out of oxygen and suffocate, the amount of time depends on size of the fish and amount of water.
Eventually the fish will also pollute the water with its own waste so even if you were constantly adding air to the water the fish would eventually be poisoned.
That’s all purely on survival, it’s very cruel to keep even small fish in small containers for long periods of times, the classic Beta in a tiny bowl. Fish we think of as fish that go in little bowls goldfish and betas require significantly more water to be happy and healthy.
Latest Answers