On February 27th of 2018 we completed a successful test growing lettuce using only vermicompost leachate in a hydroponics system.
The system was a continuous flow media bed system with the seeds being seeded directly in the media bed of this old aquaponics system. As you can see by some of the pictures the growth was great even though there were a few minor issues in the leaf tissue occasionally.
The system was also designed to return the water to the bottom aquarium (the sump) with the biggest splash possible, which oxygenates the water but on the other hand is noisy. The system was being dosed with ~50-200mL of coffee-filtered vermicompost leachate every week, and I was also adding phosphoric acid (pH down) every week to keep the pH in the range 5,5 – 6,5, since the system had a tendency to increase the pH over time. So every week the inputs were: tap water, vermicompost leachate, and phosphoric acid.
The tests I did were mostly qualitative to try and see any apparent tissue damage on the plants. Some of us tasted the lettuce and the taste was good and comparable with regular hydroponics and aquaponics, however we have little knowledge of how potentally harmful compounds added to food (such as pesticides) are transformed during vermicomposting, and how they interact with the plants growing from the vermicompost leachate. It is possible that long-term hazardous health effects from regularly consuming plants grown in this way exist, so be aware of that if you are planning your own experiments.