Why does BLF compost sometimes get very wet?

I love my Black Soldier Fly grubs, both because they will eat almost anything and when they mature I can give them to my friends with chickens, ducks and reptiles!  However, sometimes, it rather suddenly turns very wet.  The grubs don't seem to mind, though I worry that it makes it hard for them to climb out and they are not much fun to handle when they are....slimy.

Does anyone have an idea of why this happens and if there is something I can do (or not do) to prevent it?  - Amanda

It's interesting that you mention this, Amanda, because when I get them here it's always in manure slurry, seaweed tea, and other liquid environments. I always associated them with wet conditions before I learned about raising them on purpose. In my experience, when they are ready to pupate, they come to the surface and crawl up the side of the container (usually a 200 l barrel in my case), so I think the normal "exit pipe" design would work whether or not things get overly wet.

Hi Amanda, the moisture can build up over time when the grubs consume the food. There are several ways to tackle that:

First is to reduce the moisture content of the food scraps. I saw video of sone commercial BSFL operation and the feedstock seems to be ground up and dry. They simply collect sandy bsfl frass as fertilizer.  

Secondly you can try adding substrates to absorb the moisture. Compost, saw dust, or layers of cardboards etc will work. Another advantage of using cardboard is that the grubs will crawl in between the layers to pupate and you will be able to collect them cleanly.

The excess moisture won't affect the exit of larvae but if the slimy grubs bother you, simply rinse them in water before storage.