Over the years opinions have changed as to how wet is too wet for an indoor vermicomposting bin. While the standard advice is to keep your bin at a moisture level akin to a damp sponge, “standard advice” often does not translate to reality. Most bins tend to be on the wetter side of the equation. It’s safe to say the damp sponge analogy is the minimum moisture requirement for a bin. On the other end of the scale you do not want any standing water at the bottom of the bin.
There are numerous “tricks” you can use to achieve a healthy moisture level in your system. This starts with the material you input, food for the worms is the most important factor in moisture control. During decomposition organic material will release varying amounts of liquid, to control this we suggest freezing your “scraps” before using them. Freezing holds a duel benefit for feeding, once thawed the material will have seeped a great deal of it’s liquid. If your bin is too wet you can discard the liquid and use only the solid organics. Freezing also busts open each individual cell of the food stuffs, this allows the bacteria to enter the cell and begin the composting process. Worms can’t digest anything until bacteria have broken it down for them.
Bedding is your next best friend in moisture control. In a worst case, too wet scenario, in which the bin is a soupy mess, prop up one end an inch or so and pack the downward side with new dry bedding. Repeat this procedure everyday until the extra liquid is absorbed and leave the lid off. Once the bin is balanced, it’s relatively simple to keep it closer to an optimal level of moisture by using the feeding “trick” we wrote of earlier. In the rare instance that a bin becomes to dry the solution is even simpler just add water.