Quite a few years ago. Actually a heckuva long time back.
I got an old metal military wall locker and filled it with enrichened soil. Not sand or sandy loam. Make sure it can be closed or put a piece of plywood over it. They are highly prolific. During rainy weather, they crawl out. No problem. There will be plenty left and you can also pick them up and return them to their home or toss them onto the lawn. Without a cover, your patio will be covered by worms.

I fed them corn meal spread on the top of the soil. You will hear that worms can be your garbage disposal for uneaten food. Yeah, but it draws a lot of flies that will also spawn there. If you do this, be sure to bury the food. Birds and various animals dig around in it without a lid.

I finally sold the whole works to a couple of hippies from Dallas. They got arrested for using the worms to grow marijuana quicker. They used the worms to enrich the soil. They do a job of that. The cops that arrested them questioned me as an accessory but realized that I was innocent.

Been thinking a long time about doing it again.

It's not about the fish. It's about the pond. Take care of the pond and the fish will be fine. PB subscriber since before it was in color.

Without a sense of urgency, Nothing ever gets done.

Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley Rancher and Farmer Muleshoe Texas 1892-1985 RIP Grandpa