Painting does look better when it's done carefully...but taping a background to the outside of the tank can be done in seconds, can be changed later in only a few more seconds, and still looks way, way better than looking through the back pane at drywall, wires and likely more candy.
And literally any fish I have ever owned is much more intensely coloured and brighter when kept over dark gravel with a dark background. Are Flowerhorns so weird that they actually buck the trend and get more intense colours against a light-coloured bottom and background? I don't know but tend to doubt it.
Of all the pics that have won or nearly won the photo contests here on MFK, the really stunning dramatic ones are usually taken against a black background. Why is that? Do the guys who have the skill and knowledge to take those incredible shots maybe know something?