Don't worry about making the bedding too heavy for your worms. That won't happen and even if it could the worms will go to whatever depth is good for them. Your bin can be way deeper than 3". That being said red wigglers prefer to live in the upper region of their environment.

Your worms will also self regulate their population so if they get too crowded they will simply stop reproducing as much. You might consider dividing your bin and starting a second bin if you have the food stuffs to support it. Set up the new bin with plenty of bedding and an initial food supply. There are posts in this forum that address that at length.

3 inches is pretty much....no...much, too shallow for a year-old bin. Although they do ideally live in the upper areas of the materials, they need the opportunities of more depth (for all kinda reasons like escape opportunities and deeper excess moisture drainage).

Easiest thing to do: divide the bin.

chuckiebtoo

Typically, we start with about 6 inches of bedding and go from there. A typical flow through system will be at least 20 inches deep. As long as it can breathe, you can keep going deeper.

Thank you so much for your replies. You have set my mind at ease.

Sounds like you might want to consider stacking. I have one homemade setup of 3 tier plastic and each container is 22x15x7. In the beginning I just drilled holes in the bottom so the worms could move but I wasnt satisfied with that and ended up cutting out the bottoms and leaving a 3" or so lip and cut out some hardware cloth to fit. In that way it resembles the worm factories. Just a thought.