#ed_op#DIV#ed_cl#Wow somthing I can answear. Mind you its not as good of an answear some some other people will give you. But a powerhead basicly makes your water move. Kind of like it does in the ocean. Also some of them help with undergravel filtration. They are also very important for some coral. Hope that helps some. I sure others will come and give you more info.#ed_op#/DIV#ed_cl#