Is this gonna work out?

So i wanted another pet but my gramma said no. So i was really bored, I went out in the yard and collected a few pillbugs and put them in a 'bug habitat' A got a while ago. It's basically 1 gallon tank/cage combo with some hiding and clmbing areas and all that. So i put about 3 cm of sirt at the bottom, misted the habitat to keep it moist, put a rocks, some bark, and dead leaves in there and added 4 pillbugs. Is this ok? the only thing im not really sure is what to feed them. So far its been dead leaves and tetramin flakes.(fish food) Also, what can i give them for calcium? my gramma wont let me get the calcium dust...