I will try and ask around cause when we were first building this up, we did not find any garden stores who know about terrariums unfortunately. Until I change it, i was thinking of watering with bottled water for most of the time and then some tap water every now and then (since you suggested that a little bit calcium in the water might be good for coco fibre). Do you agree? Also, we do not have the same problems on plants which are in pots (but as you mentioned, these have drainage so that could be the reason why). Thanks once again
