Floating bacteria, or bacteria in amounts large enough to be seen floating in the water column is something to be avoided at all costs. In fact, I'm willing to bet that you can smell bacteria at that level of concentration. Luckily, most of the beneficial bacteria that uptake nitrogen in aquaria are content to form colonies within solid objects, including gravel and soil.
But here's the thing: plants and bacteria compete for some of the same nitrogen products. And one of those, ammonia/ammonium (I'm not sure what the difference between them is) is metabolized by plants more efficiently than the by-product (nitrate) that is left over after certain bacteria get through with it. So, the whole idea of a Walstad tank is to give the plants a headstart on the bacteria in order to give them first crack at the available ammonia/ammonium.
And, yes. Lucky bamboo are great at consuming ammonia/ammonium before it gets converted to nitrite and then to nitrate by beneficial bacteria. @dwalstad
writes extensively about how certain terrestrial plants that can survive under wet conditions, have an "Aerial Advantage" over aquatic plants in that they can perform photosynthesis above the water line while processing huge amounts of nutrients through their root systems beneath the water; much more than aquatic plants.