[Myka]

They won't fill as well as you'd think they would. The average MH bulb will cover a spread of 24x24". T5s will be 24", they aren't going to cover the length of the tank any better! Even if you stagger them...you'd end up screwing around a whole lot, plus you need to squish some T5s in there for actinics anyway. The cost of a set of retro fits to put more white lights in would be about $75 less than replacing your DE with an SE socket, and changing to a Lumenarc fixture. You'll get hella more par running a SE bulb off that HQI ballast. You could always just stick with what you have for now, and if you decide you don't like it, then just upgrade to the SE socket, and buy a Lumenarc. You will need some actinics though...looks waaaaay better.