when i got a 30 gallon tank i moved 1of my 2 filter to it and all the water in the 10 gallon. i didnt want to mix the old gravel so i left the 10 gallon outside and all the ornaments in it. after about 2 days i went back to it and holy it smells worse than anything i ever sniffed. i attempted to clean it but the stink wouldnt go away. i will plan to fill it water and then vacuum the gravel. after i would put the filter on and change 100% of the water everyday. would that help? any ideas would be helpful