my fish tank smells horrible--help!

[ELECTRIK]

i have 3 tiny spotted puffers, they have been living happily for 3 months in a 3 gal
setup, they get along better than any fish ive ever had(which is rare for this breed)
they constantly stay together and even share food , i purchased a 50 gallon tank but have not set it up yet because of the odor problem in the small tank.
Ive tried everything i can think of, chemical treatments etc. and still it smells like nothing i can even describe. just in case this requires a major overhaul to stop i want to know before i set up the 50 gal, as it will be much more difficult to make drastic changes in that size than in my little one, plus the little tank is stinking up my apartment--i have to sleep with my window open , I can only imagine how bad 50 gallons worth of that stink would affect me
please help

 

[smb]

How often and how much are your water changes/gravel cleanings? What filtration do you have and how often do you rinse it?

Do you have sand or gravel?

 

[akhtar]

i had the same problem, coz there was to much amonia, and when the tank was funny cicled it was ok