My fish is sick, HELPPPPP

Question
What about his fins? Its not that hot here..only in the high 20s. And when hes at the surface(with is always) Hes not breathing off the top..Hes just floating there kinda. Hes dorsa fin is always down. And my other goldfish is fine. Also i have a 6.5L tank, If i put anyone goldfish in there(aside from the two) will it be overcrowded? What do you recomend.
Thanks again :)
-------------------------

Followup To

Question -
HELP! my gold fish is hanging arownd the top with his fins all put together and they look un-helthy. I have two goldfish and the second one isn't picking on the sick one(however his fins look like it)Also he wont eat. Whats wrong with my poor fish? Is there something i can do? Please aweser me ASAP, my fish's life depends on you!

Answer -
Hi Nadine,
Thanx for your question.  Is it really hot?  It has been in the 100s here for over a week and this takes the oxygen out of the water and weakens the fish.  They start gathering at the top of the water to breathe.  The overly warm water makes them sluggish.  If you have a bubbler make sure it is working.  Add some oxygenating plants if you don't already have any like anacharis, cabomba and some floaters like water hyacinth and water lettuce to help keep the water clean.  When things cool down the fish will get better.  I hope this helps.
Tom

Answer
Hi Nadine,
Thanx for the follow up.  The fish may have a swim bladder problem.  If you don't see any scum or growths on the fish and it is not sucking air then the fish may have a swim bladder that is not working correctly.  The swim bladder helps the fish swim up and down in the water.  Remove the fish and put it in a separate container just in case it is infected with bacteria or virus.  My guess is that this fish is not long for this world I'm sorry to say.  As I said, isolate it in a separate tank with no other fish and deprive it of food for a few days.  This will not harm the fish.  Sometimes they can become constipated which inteferes with the swim bladder function.  By depriving them of food for a few days this will sometimes cause the impaction to dissipate.  I hope this helps.
Tom