Hey mate ive had a black flounder in a tank for the last 7 years,Im pretty sure he was a boy as he LOVED fighting and had bite marks on his fins,rips,tears and half his tail was bitten off,His favourite food was Inanga sadly,lol,He was definitly the king off the tank-We called him "THE GENERAL" ...Unfortunatly-he passed away 2 weeks ago i feel maybe because his time was up,Trust me i was gutted...Anyway i stay in Otaki and go to the river alot and i have seen at xmas time lots and lots and lots off Black Flounder-The best viewing was 2 dark blue and a pure white Black Flounder who i call Zoom Zoom as he comes close to you but is smart enough to not get too close/but hes there alot...thanks guys.