silkworm castings - does anyone have worms strickly for the castings?

So I have a lot of plants and I was thinking of getting some silkworms and setting up an old fish tank to breed and collect castings. I was just wondering if anyone else has done this.

I was also wondering if I could adjust their diet to adjust how effective the castings are.

Silkworms are actually caterpillars so they turn into moths, but they love white mulberry leaves while young !

Why not get some red wigglers tho, they will multiply and multiply and multiply
And you can add them to the garden at any time with no fear they'll fly away ever