首字母whenpeoplethinkaboutsourcesofwaterp（1）,theydonotusuallythinkoffishfarms.However,asthedemandgrowsforfishtoeat,then（2）offishfarmsisincreasing.Insomeareas,theyarebeginningtohaveenvironmentalproblems.I

　　首字母whenpeoplethinkaboutsourcesofwaterp（1）,theydonotusuallythinkoffishfarms.However,asthedemandgrowsforfishtoeat,then（2）offishfarmsisincreasing.Insomeareas,theyarebeginningtohaveenvironmentalproblems.I（3）fact,whenfishareintheirnaturalenvironment,theydonotpollute.Butinfishfarms,theenvironmentisn（4）natural.

　　Thereareusuallyl（5）offishinverylittlewater.Thismeansthatthewatermustbechangedveryo（6）.Andeachtimeitischanged,theusedwatermustbethrownaway.Itisusuallythrowndirectlyf（7）thefishfarmsintoariverortheocean.Andthatchangesthechemicalsoftheriverorcoastline,sotheplantsandanimalslivingtheremaysuffer.