thanks for ur quick reply. i'm asking this question after reading julian sprung's "algae" book p.29 which read "Ctenochaetus spp. are rather prone to breaking down with Amyloodinium, aka velvet disease, which is actually caused by a parasitic dinoflagellate." then i thought these dinos are the same. thanks for clearing that up.
i'm planning to add a kole tang to my 150G. after last ich attack, i fallowed my tank for 3 months, quarantine every new coral including inverts for a month and treat all fish, incoming fish with seachem cupramine. so the new kole tang can't get velvet from poor water conditions,etc. am i thinking right?