I plan on switching Mitch over to a staple of Phoenixworms, but I’m not sure how many to feed each feeding. I plan on giving him the BSFL on Sunday and Wednesday, with supers on Friday. He’s 7-9 years old, 16 1/2 inches long, and about 304 grams
At that age he should be eating mostly veges. Offering some BSFL as a treat or as a meal once or twice a week is OK as you've planned. Give him all he wants but be sure he chews them well and they aren't passing through undigested. Since they are so small he may be able to go through a lot of them so just try and moderate how quickly he eats so he chews them a bit.