Yeah, when he gets bigger, you can start fasting for a day or two. My larger TSN gets a full tummy every couple of days. Well, he did until he went in with my rays. He now plays cleanup crew everyday.
My baby 3" rtc gets bloodworms twice a day.
When they get around the same size, both cats will be going in a pond and will get fed large portions and then fast for two days.
I would also avoid beefheart as a staple. Every now and then would probably be alright, but fish can't digest mammal fat like we can. I would try to get your fish on shrimp, tilapia, and other seafood. Its cheaper than those little cubes by a long shot. I would cut mine up and mix it with earth worms. That seemed to do the trick with all my larger fish.