I love thin bars, but in my experience they are the most shy of all the datnoids .... your lucky that yours is stable, mine only get stable when they feed .... I just did a tank switch in the hopes that my thin bars come out more often, so I'd say its the nature of the fish ..... taking decorations out may force him out, and he may find that he likes it, or it may stress him out, but its an option to try .... other than that not sure what to tell you, its what they do
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