Just a thought, since the videos say arowana's have special eyes to see above and below the water, could putting them in tanks have any effect on this which would then result in drop-eye? This doesn't really explain why black's have a lesser chance of getting drop-eye though. Asians kind of live in a different habitat (I'm assuming cos they are on the other side of the world) but it still doesn't explain the blacks..
Awesome videos, well worth watching!
Awesome videos, well worth watching!