smell

Both of my HOBs... identical... one in a 10 gallon tank with a betta and two nerite snails and one in a 5.5 with only neo shrimp (I Know this is a betta site but it involves the betta tank) smell. For sure the biomedia (the stones in the bag on top) smell. Pretty sure the rest of the media...

please read this topic for further information https://www.fishforums.net/threads/gravel.405485/ gravel was their Premium aquarium gravel , brown natural colour store admit its possibly deadly to your fish.