Every time i use moss collected from outside it fouls up the terrarium. I end up with something chewing holes in my plants, foul smell, mold or it simply dies and has to be removed anyway or it molds
Do you add springtails? You could also try soaking the moss in RO water for some time to kill off pests before adding it to terrarium, and then add the springtails afterward. Some amount of die off is normal when you transplant any plants, including moss, but they should recover if given time and the right environment. Keep trying.
