I am not sure on a King Betta, never had one and then I don't feed much store bought food anyway. IMO feeding also depends on the type of food and size of the pellet, you should post this on the forum to get a better answer...sorry I couldn't help more....
I'm really worried about Alex :[ I was hopeing that you could help...! He is eating normal...and he's active and being his happy self but I noticed a dark black spot on his body that is just a black puffy spot...I really have no clue what it is! Is there something wrong with him...? I'm really worried about him!!
I wish I could help you out with this question, but I make most of my stuff and some of my store bought stuff is pretty old and I don't use filters on my tanks 3g and less.
You should post this on the main board, there are lots of pretty smart folks on this site that would love to help you out.
Sorry I couldn't help