pounds are often cleaned out in fall, though if you have the biology right you dont have too. I have a filter, screener and waterfall. I use standard pond bacteria, algae block cubes, barley straw extract, and sometimes pond sludge remover (bacteria) though not this year at all cause it does not need it.
get the stuff online as the stores will way overcharge. assuming that you are on-site spend your time trying to perfect the bacteria balance and algae control rather than on mechanical cleaning. one of the biggest mistake people make is to either not control the algae at all or to kill it now and then, because all that dead algae has to sink to the bottom. dead and live algae is what usually clogs the filters.