It could very well be a sterlet. Some have been available in the Ohio area recently. I have no experience with sterlet, but have kept white sturgeon. The most common problem people seem to have with young sturgeon is getting them to eat. Frozen bloodworms are a good food to start with. My sturgeon was quickly weaned onto foods like freeze-dried krill and floating pellets. I sadly lost the baby I had when the water temp. got too high in the summer. At the farm where I used to work with them, they are in well water that always stays nice and cold for them. For the sterlet, I doubt brackish water is really necessary. White sturgeons can be found in full marine conditions, but do fine in freshwater as well.
As for the swimming, young sturgeons (and even those several feet long) do all kinds of crazy things for no apparent reason. One of the biggest at the farm enjoys laying on her back for hours at a time and people ask if she's dying. Mine always went into a "death spiral" at the surface after the tank lights were turned out. Many also get excited and breach and start doing a sort of dolphin tail-walk at the surface. The big ones at the farm love human interaction and occasionally show off for visitors. They are really entertaining fish. Good luck with him
