With a large surface area/size ratio - Nano-balls out-perform any bioball in the market. You can fit almost four Nano-Balls in the same space it takes to fill one standard bioball. Known as an excellent media for growing bacteria, the small size allows them to be used in almost any type of filter. You can place them in a power filter, canister filter, wet-dry filter or even directly into your tank. Each package of 1/2" Nano-balls includes a polyester mesh bag to keep those buggers contained! The large spatial areas inside the bioballs allow more water to flow through the media with ease - keeping it clean and efficient. While other medias clog and channelize, the plastic construction makes them non-clogging and totally inert. Unlike other plastic media, we made our bioballs negatively buoyant. So instead of seeing them float away, they can be placed in the area of your filter that you want them. Easy to rinse and clean, they are lightweight and will not degrade over time. Two Container sizes available: - Nano-Balls 600 ct. ( 1/2" dia. ) Supports up to 30 gal. aquarium. - Nano-Balls 1,000 ct. ( 1/2" dia. ) Supports up to 50 gal. aquarium.