When I buy plants - which I do quite often due to my destructive pleco - they come in little plastic pots with the roots wrapped in some kind of sponge. Should I keep the plants in these pots or plant them straight into the gravel. I've noticed that sometimes after a while, the sponge disintergrates and starts to smell like rotten eggs, (some form of sulphuric whatever) and I have to de-pot them and clean up the mess Yet some of the plants are fine and have been living in their pots for months with no smells or anything. Any help as to why some start to smell and others are fine