OK, So i ordered my plants and they are arriving today. However, the store owner told me, explicitly, that terrarium growth could be dangerous for these plants. He is telling me that in his experience, terrarium growth often works for a couple of months and then fail because of various components like salt in the substrate, he noted that cocofiber is not good for the plants long term, especially the venus fly trap, and that terrarium temperatures can get too hot for the plants.
SO I have opted for a pure sphagnum moss substrate, but now I am concerned about the nutrient content of the substrate. Will I need to feed more because the substrate has no nutrients of its own now? I know carnivorous plants don't usually take a lot from the substrate but they do still work on some nutrients and I know that sphagnum moss does not have a lot of nutrients, if any, since it kinda just works like a sponge?