I have all sizes of BG from both last years hatch and this years eating pellets. All the way down to inch long BG "tasting" it with 1.5-2" BG gobbling down AM400.
If you want the young ones to catch on quick, provide the right size food. My small BG would always peck at the larger pellets and get a little that way, but the larger BG would clean everything up before the pellets got soft enough for the small BG to get much.
When I FINALLY got my first Aquamax order I had a few bags of AM400 just to try it out. I had no idea it was so much smaller than AM500 would be, but it is very small. Started throwing the AM400 very near the shore while throwing a mix of AM500 and AM600 out further from the bank. The little BG took right to it and within a couple weeks would line up at the shore line and look at me on the 4 wheeler (that I feed from) waiting for me to throw the feed to them.
Also feed trained about 5 small red ear slider turtles without the intention to do so. They were so cute and small I just had to keep feeding them. They also would swim up within a few feet of the shore and wait till I threw them feed. Funny.