IMO, none. I hate those things. but they are decent for a snail, I just hate picking up all my frags after they've been knocked over.
For hair algae, your best bet is going to be a vairety of algae eating critters instead of alot of a single type. Best hair algae eater I've ever owned was a baby queen conch, but he ate HA in my tank, but not in somebody elses.
You can go to sites such as liveaquaria.com and similar to see what kind of numbers they utilize in their clean up packages, to give you a rough estimate.
I honestly wouldn't stick more than 5 of the turbo's in my tank. I'd use up a bunch of ceriths, nerites, maybe fighting conch, astrea's, and nassarius. Some of these won't touch the HA, but algae is only one reason to have a cleaning crew.