Won't do much for indoor containerized plants other than muck up the drainage. Worm castings are great for adding to a garden but do not work well for plants grown in potting soil. You would be far better served by using a proper liquid fertilizer. If you really want to use the castings, make a tea out of them. But you will still most likely need to supplement with a fertilizer.

In the same vein Pam was pursuing, container media are more about structure than their ability to provide nutrients for the plant. That's the grower's job when it comes to container grower. If your soil is poorly structured to the degree it won't allow you to water correctly, that is to say so you're flushing the soil of accumulating salts and correcting skewed fertilizer ratios in the soil solution as you water, fertilizing efficiently is extremely difficult. OTOH, if your soil is well structured so you can water correctly, fertilizing is monkey easy. Following that line of reasoning leads to the idea that you would be best served to ensure your soil allows good watering practices and to avoid doing things that compromise that ability - especially since there is nothing essential in worm castings that can't be found in a high quality soluble synthetic fertilizer like Foliage-Pro 9-3-6.

Al