My 20g riparium is running without a filter or powerhead, heavily planted, heavily stocked with a juvenile BN pleco, a molly, six neon tetra, 3 amano, umpteen cherry culls, pond and malaysian trumpet snails (only a few huuuge ones, not enough food for them to reproduce thanks to the...) endless parade of females and fry from the resident black bar endler colony. Not a speck of algae, not even green dots on the glass. It gets a 10-20% wc every other week, more from habit than need. Substrate is fluorite with a scattering of aquarium gravel and small river stones, hardscape includes a variety of driftwood shards (3-4" long), a big hunk of dw for the pleco's cave and a large multi-branching bit of manzanita. No lack of surfaces for BB, especially when you add in the thick mats of aquatic roots from the riparium plants.
My planted vases (3g and under) are tech-free. Including a heavily stocked 2.5g vase with 8 cherry shrimp, a gazillion scuds, a male/female breeding pair of hybrid endlers and anywhere from 4-14 fry at any given time.