IMO there are two things I’ve done which caused a colony explosion this year.
One is a warmer diapause inside my house. I keep them in a room that is 66-68, cool enough that they enter diapause but imo places less strain on the colony. I had ZERO worker deaths from diapause and only 15 total bodies in the outworld over the past 2 years. Second, as already mentioned, tons of protein sources. I use cooked chicken, pork, egg, live insects like spiders and fruit flies and then a good supply of maple syrup, ant nectar and ant juice.
This C. castaneus colony went from 3 workers and a queen 2 years ago to this large colony with several hundred workers. Both sides of this nucleus habitat are filled up and now they’re overflowing into the outworld. Here’s a pic of the colony and the brood pile this spring after they were a few weeks out of diapause.
And here is a pic of the colony. There aren’t as many ants on the front due to the light that shines on it and they prefer the back portion better because of that.