I noticed a black spot on the back of my banjar red arowana. Do anybody know what this is and the cure??
Can't tell 100% for sure from the pic but it looks like it got a little injured and a top scale was knocked off. If that's the case it'll heal over time by itself, though do keep the water clean and watch for possible secondary infection. Some might add a bit of salt and/or catappa leaves to help with the healing process.
The scale itself should come back pretty quickly (about a week), but for coloration/shine to return it can take quite a bit longer, just have to be patient.