Hm...well, if the chaeto were growing, it should've taken care of the phosphates. Try switching to a light that's 6500k like the bulb I posted above. Also trim away the dead parts. Is it tumbling around? Chaeto likes to tumble a little bit (not super fast, but just rolling around). When I put a powerhead in my sump and tumbled the chaeto, it really started growing more (in my 125g).