Anytime you do a hardscape layout, you want to check where the dominant lines are drawing the viewers eye and make they work in your favor.
In this case, that chunk of driftwood is the dominant piece and it's line is a diagonal from the center of the tank out the left hand side. So, your eye is most immediately drawn to the bare center of the tank (blah) then pulled up and out to the left where it'll notice... well, something other than your fish tank!
I'd play around with the positioning of the wood to get the dominant line to lead into or across the tank. Easiest fix would be to leave the wood in the same orientation, but slide it over to the far right side.