I wouldn't leave it much longer than 3 or 4 mins, peas can get messy! 1 or 2 should be plenty for 6 minnows.
Goldfish and minnows don't really mix, a fully grown goldfish can easily eat a minnow. Also goldfish get so chuffing big that not many people have the space for the size tank they need. That's why I like minnows