Man, I feel this in my soul. I started with 8 in a 3 gallon and now the glass is basically carpeted with them, no clue when it crossed the line. The java moss moving thing made me laugh because that is exactly what mine does, it just becomes one big shrimpy blob. My honest rule has become when I can't see the bottom anymore or when the babies start getting picked off by the bigger ones, that's when I know it's too packed. 47 in a 2 gallon is wild though, you're probably already past the line and just in denial like the rest of us. I'd start pulling some out soon before the water quality starts swinging on you.

Did you notice the mold came back at all after the springtails cleaned it up? I had a weird thing happen with my first jar where the springtails crashed after a few months (I think I let it dry out too much, my fault) and the mold stayed gone anyway. Maybe the springtails ate something the mold was feeding on, or maybe the mold just ran its course. My buddy's open jars do fine but he also lives in a dry place, so airflow and humidity might matter more than the bugs themselves. Anyway I still buy a culture for every new build now, mostly because watching them swarm a piece of mold is weirdly satisfying.