This is what I understand. A wet/dry is divided into two sections. The 1st part is where the drain leads into a filter pad then goes through the bio balls. This section is called the bio tower. The other section is called the sump. Im assuming what they are suggesting, is to remove all the bio balls. Or...theres more to what you quoted. _________ 9YR OLD 90G 30G w/d Mag18 150G skimmer 692w MH,yel&kole tang,foxface,midas&convict blenny,B&G chromies,Blk/yel fin chromie blackcap,nemo,neon goby,6line; Blastomussa Merleti,Acan ,BUBBLE,Torch,LTA, Goniopora(2), Acropora(2),Brain, Moon, assort zoas, yel& G star polyps, R&G open brain, P&B ricordia, montiporas, cup&candy corals, enias,B/G mush,flower ane(2), cherry red mussa, dusters,cleaning crew |