At that size, large hi-quality pellets would be good as a staple. Frozen bloodworm will bulk them up very quick, but that could get expensive in the long term... Frozen shrimp from the grocery store may be cheaper & easier to get than bloodworm, but its not quite as much protein per bite. Throw in a hunk of cucumber every now & then, too.
Just FYI, I found 1mm NLS pellets at Petco today. Thats some serious hi-quality food & my loaches love it. You may need to order larger pellets for your monsters, but I thought I'd post it up.