I'm having a problem where my 5 gallon tank is stinking like a swamp and it's beginning to get fairly strong despite constant water changes and gravel vacuuming which we do once every 5-7 days.
The amonia level is at 0. The PH is at 7.0.
The filter cartrige looks fine and is only 3 weeks old.
We don't feed flakes, just pellets (and those are in the water for less than a few secconds given at how quick the betta eats them) so there shouldn't be any decomposing food in there.
I always make sure that I give the gravel a good vacuuming when I change the water.
Yet despite all this, the tank is getting a very strong swamp smell to the point that it's beginning to stink up the bedroom where it's located.
I've had other fish tanks in the past and none of them ever made an odor like this.
Anyone have any idea as to what's going on and how to remedy the problem?