Bio Balls????

wat exactly do they do???
wat are they made of?
do they go away over time?
do i have to replace em every so often?
i ask this bcuz iv never had anything with em and i recently got a tank with a built in sump in tha back and idk Squat bout sumps and bioballs!!
plz help or give me any info on em
plz and thank you

made out of plastic. bacteria grows on them. you have to clean them every so often. should never clean them all at once. They don't go away. Never have to replace them. I use them in a wet/dry and the drip/trickle of water with the extra oxygen from not being totally submerged allows more bacteria to grow on them. They are also specially designed to create a better bacteria growing surface than other media. Just my .02

great information on em!!!
Thanx bro!