It has been my experience that a lot of peoples personal fishtanks have a bit of a smell to them. Putrid is not the word I used.
No, if your tank has any aroma what-so-ever you fucked up.
Go sniff a river or an ocean.
Does it smell like your boyfriend's butt?
I had two 55 gallon standard tanks and three 5 gallon nursery tanks.
I was growing Apistograma Ramerisii . . . . .
(now called Microgrophagus Ramerisi because Pluto is no longer a Planet
)
Got to the point I couldn't get rid of them fast enough.
Never did my tanks have any aroma.
Well except when I built my first tank when I was 15.
I discovered fish keeping is actually filter keeping.
Also, I was 15yo,
So to keep everything surviving I built a filter system out of two 55 gallon food grade plastic barrels, a manifold of PCV valves, three pumps, bliss.
Then the pet shop closed about the same time my life trajectory misfired.
But at no time did I accept a fish tank should stink.
Just some advice . . . when there is a string of poo sticking out of you fishes vent,
you are over feeding.
A 2.75" fish has a stomach that will hold about 3 grains of rice.
Fish, like humans, will eat themselves to death.
Err on the side of starving them.