Cut the leafy lettuce scraps up into small shreds, so it will tend to float rather than sink ..... especially if you want to teach them to come to the top for feeding - at first I made the misteak of getting sinking food, pretty soon, they wouldn't feed off the top at all!

I'm not real fond of the commercial fish foods, since they put all kinds of chemical garbage into them for filler - look at the labels and determine how much protein and fat content, as well as drugs, land animal ingredients, etc., are involved so you can make an informed judgement as to what quality of food you will be eating when your AP foods and fish are harvested and therefore avoid the ones that are all junk, drugs and filler. Just consider this: all of those drugs, chemicals, etc., in that fish food are floating around in the same water that provides nutrients for your veggies in the grow bed

Aquafarms Fish Food is no longer in business AFAIK, but their website will give you a lot of info on feeding, as will Jim's Fish Shop - (also out of business AFAIK)
AFFF - Clik
JFS - Clik

Just my 2 centavos ........