I did this earlier last week and forgot to post. Have twice now fed red wiggler babies to my fishes. It will probably only be a treat once every month or so, because the only time I easily find baby worms is when I'm sifting compost out and doing a bin transfer. I'm still satisfied using the sifter but need to make a new one out of sturdier plastic- after only three uses this one is falling apart. I'm glad I thought to do it now, because I'd left the worms alone too long. Hadn't fed them in a week or two in hopes they'd consume more bedding, but I also forgot to get in the bin regularly and fluff stuff up. With mild neglect the bottom of the bin got damp and compact- so the vermicompost stuck to itself, not loose and crumbly. Which meant I didn't get a lot out- less than a fourth of a bucket even though I sifted the entire bin.
As is, I only had enough vermicompost to side-dress the broccoli and swiss chard plants in the garden. They looked the most needy!
Then I fed the fishes. I have not been able to give them flies anymore. Used up the last of my frozen jar near the end of winter, and this summer we don't have a fruit fly problem in the kitchen. That's great- I think because I've been keeping counters/sinks cleaner, and have a new cover for my scrap-collection container under the sink. My husband is very pleased. But I miss being able to feed fruit flies to the fish!