ok that half cut me off...but in my 10 gallon cycled tank it smells not horrible but not good in the tank.
I do water changed about every 3rd-5th day and I have 7 fry, one cory catfish in it so I don't relally know why it smells..
If you have fry that means you feed them a lot - baby fish need to be fed a lot in order to grow and develop properly. What comes with a lot of feeding are a lot of wastes and probably a lot of food rotting and giving your water a bad smell. In a fry tank you should be performing probably daily water changes. What kind of fry do you have? In my 10 gallon tank I had 11 angelfish fry, and for the first 2 months of their lives I was performing 50% daily water changes. Water changes should remove your smell, as well as nitrates that are not healthy for fry.
What you can also do (if you don't already do this) is use activated carbon in your filter. It should remove the smell.