How long has the fh been in the tank? Sometimes it takes months for them to settle in. Especially if they are young. The more fish in the tank the less he will feel like the only "prey" in the tank. Some of my breeders who sit alone in smaller tanks never leave their cave. As soon as I toss em in the big tank with more distractions its like they become different fish almost immediately after joining the "school" of others.
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