I wouldn't say 5.6wpg is inadequate for a condy, the fact that it's in a hex tank may have something to do with it climbing though since hex tanks tend to be taller so the lights have to penetrate deeper. Your right WPG
isn't the only thing to look at, depth is very important as well. 3wpg over a hex tall tank wouldn't be the same as if it was a standard tank. And, condy's actually like more light than bta's (and is why I suggested a bta and the others only a secondary suggestion) but I stand by my advice that a bta would do ok.