I thought, too of adding a pinch of compost. All you have to do is inoculate the mix as long as there is organic material in it. The microbes will reproduce, break down the organic matter and feed it to the plant. One reason I tried the inoculant was because I was having so much trouble with root rot on my Streptocarpus. Evidently the good bacteria will compete with the bad. The survivors are now thriving.