"hiding under driftwood" can mean a lot of things. If he's lethargic and has little appetite, maybe he's sick. If the driftwood is the only hiding spot for him in the entire tank, he might need security from more hiding places and areas to rest. If it truly is the filter flow you should start looking into alternative filters or ways to lessen the flow of your filter.
To lessen the flow of your current filter sometimes stuffing more media into the filter can work. You can also try the soda bottle method (I use this).