Why is my fish gasping for air at the top of the tank?

Related questions

1. Is it good to have fish tank at home?
2. Do fishes need oxygen?
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5. How much does it cost to go to the aquarium?
6. Can fish die if the tank is too small?
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Tags

1. #warmer
2. #however
3. #several
4. #factors
5. #dissolved
6. #enough
7. #water
8. #gasping
9. #could
10. #surface
11. #levels
12. #cause
13. #oxygen
14. #should
15. #highest
16. #holds
17. #contains