At first, I have to admit, I thought this was the worst idea ever. It sounds like a recipe for a pH nightmare. But then I remembered that coffee shops give out the grounds to gardeners, so I decided to give it another look.
Here's what I found out about the coffee grounds idea:
*Yes, it is helpful. What it does is add more nitrogen to the soil, but it does so more slowly. This allows the plant to have what it needs, nothing more and nothing less.
What you do is put this until the soil before you water the plant, and then when the plant is watered, then it starts to get the nitrogen.
You can also use it as a fast acting fertilizer when you add the coffee grounds to a lot of water, diluting a half a pound of coffee into water and then letting it become room temperature.
This will cause the remaining liquid to be a great natural fertilizer, though add sparingly, just as you do with any fertilizer.
I know that outdoors you can add egg shells around the base of a plant to repel pests, but I'm not sure whether that would work indoors for MJ. Never hurts to try, I guess.