Big tank, small solo fish, bright lights, no real cover in the tank. That's the problem imo.
Add the convicts sure that may help, (wouldn't go for any schooling/livebearer fish- sure to be eaten with a piscivorous cichlid like a dovii) but I think adding cover/decor will also be important to helping the dovii become outgoing. Fake plants with suction cups that go on the top will help alot. Like
duanes
explained the hiding is instictive to avoid predators, and especially if there is nothing going on in the top half of the tank, they feel like a sitting duck waiting to be eaten. And yes, dovii are usually pretty shy fish until about a foot long anyway.
Here's an example of what I mean by cover in the upper reaches. One of my tanks from a few years ago. More subdued lighting also helps.
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