I have a hair algae farm in my overflows. Nothing in the DT though. I suppose it helps export nutrients but I decided I don't like it. I pull out tons of it all the time.
There's a guy on eBay that makes AGA/Aqueon style overflow covers. They look very well built so I ordered a pair for my tank. I got sick of my Yellow Coris Wrasse overflow jumping anyway.
On the other hand, you can let it grow and you have an built in algae scrubber. Harvest it when it starts to block the overflow and let another round grow.