How do you prepare vegetables for these fish?

I have 5 mollies, 2 cories, and a betta (in a different tank). I tried summer squash on my mollies, but they didn't seem to be interested in it. I have some peas that I was thinking on trying for my betta (he has been a little constipated...) but I don't know how to prepare them. Any suggestions on different vegetables for my mollies and how to properly prepare them? (I probably prepared the summer squash wrong, hence why they didn't like it very much) Thanks!