Just wanted to clear some things up about proper use of different types of filters and media. First, to properly use bioballs, you need a sump of some sort and a chamber for the bioballs which is NOT UNDERWATER, some tanks have these built into the back, but if you just have a plain rectangular 10 to 30 gallon tank, you don't really want to use bioballs, just get a biowheel or simple sponge filter, or make your own air-driven sponge filter out of some foam, pvc, airline tubing, and air pump. Bioballs are meant for wet/dry trickle filters where bacteria can grow aerobically which allows a greater rate of biological filtration than bacteria that are always submerged in the water, so if your bioballs are under water, or floating in the water, they're really not any more effective at growing bacteria than your gravel. Many lfs do use bioballs, but you won't see them because they'll have a huge sump and bioball chamber hidden from view. If you have a biowheel, don't worry about the bioballs, the wheel that comes out of the water and into the air has pretty much the same concept as a trickle filter, exposing the bacteria to an aerobic environment. Also, when you buy bioballs, they do not come with bacteria already on them unless you get them from someones actively running bioball chamber. The same goes for biowheels, filter sponges, and any other filtering media.