Here is a pic of one of my Pinguicula cyclosecta in a 3.5 inch pot. The plant is transitioning to winter leaf form. The media is pumice with a little silica sand mixed in. The dark surface on the media is a film that forms, over time - it is likely a mixture of bacteria/algae and other adventitious microorganisms (perhaps even some blue green algae/cyanobacteria, which fix nitrogen). These are growing under cool-white fluorescent lights, about four inches from the leaves, 24/7/365, and are kept soaking wet year-'round. The crown split earlier in summer leaf form - they will eventually grow apart, and small plantlets have formed underneath and are poking out around the edges of the canopy. Fed weekly with dried powdered bloodworms and dried powdered locally captured insects. Also with a bi-monthly spritz of 40-80 ppm solution of Peters 20-20-20 soluble fertilizer with trace minerals. When I spritz, I wash the insect powder between the leaves and into the crown of the plant. The insects exoskeletons are made of chitin, which promotes chitin eating bacteria. Since these plants are prone to crown rot, promoted by nematodes, and nematodes egg shells are made of chitin. Hypothetically using lots of powdered insect remains, suppresses nematode populations, reducing the incidence of crown rot. Also chitin feeds beneficial fungi, such as Trichoderma species.