Well I have used a canister for two years,with corals,even the guys at northlands pets do,it just a major misconception that it is a nitrate factory! Over feeding is the major problem cos leftover food gets sucked up by the intake pipe of the canister.So personally I add a thin porous piece of sponge into the intake pipe that way water still can pass through,but debris cant
As for clean sea water in durban,lol no way! I tried that and big mistake!parasites like crazy.best place is south coast,has clean,clear water.The boyu tank was R9000,but retail is around R12,and I wudnt mind setting up a 4ft to 6ft tank,just buying salt will make hole in my pocket