aquarium fish

Question
QUESTION: one of my four fish keep swimming to the top of the tank like he's looking for food, keeps swimming straight up like he is eating, he is not relaxing at all like the other fish, keeps going to the top of the water all day and night, why is he doing this

ANSWER: Mickey,
How long has this tank been set up? what kind of fish is this?  What size tank?  What are the water parameters?  Without this information, I cannot even begin to guess.  If you get back to me about this information, I will help you with your question.

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QUESTION: my tank is set up for 5 yrs now, i don't know the name of the fish, but i have three of them, the others don't do this, they are pink, a light pink, and the size of a gold fish, it is a 10 gallon tank, i don't know what water parameters are, the fish keeps going to the top of the tank and he surfs the top his head is up and he keeps going across the top of the water, have you any idea why?

Answer
Are the fish 5 years old also?  If they are not goldfish, a lot of tropical fish only have 5 year life spans and could be old age...another possiblity is he wants more oxygen.  how often do you change the water?  What are the ammonia, nitrite and nitrate readings?