Aros are top-water fish. as he gets bigger and braver he might explore more often but he will spend the majority of his time near the top. Its a good idea to have floating plants or driftwood. Some cover at the surface will help him find his courage. I have a 9" silver in a 30" tall tank. Driftwood extends from the bottom of the tank and breaks the surface of the water. My aro rarely goes into the bottom third of the tank but he seems to explore the branches quite often.