I'm not sure any fish eat hair algae. There are various fish that eat microalgae (bicolor blenny scrapes algae off the rocks, "kisses" the glass) and various tangs eat various macroalgae but none of mine eat hair algae. I have a yellow tang and regal tang in one tank, a purple tang in another. The yellow and regal definitely don't eat much, if any, hair algae. The hair algae in the purple tang's tank is higher up than it feeds so I'm not quite so sure. Of course if the tangs were starving they might behave differently but that is cruel IMO (it is important to feed lots of algae for tangs, I cringe when I see the skinny yellow tangs in some LFSs and office display tanks).
I've read many posts on lawnmower blennies and foxfaces and there are lots of folks who say neither of these eat their nuisance algae!
IME the best solutions for hair algae include pulling it by hand, nutrient control and perhaps inverts (snails, crabs). Nutrient control consists of (1) not overfeeding and (2) exporting nutrients (growing and pulling macroalgae or growing and trimming mangroves, for examples). And of course water quality makes a big difference--tap water often has phosphates that "fertilize" algae. I found using RO made a noticable difference when we switched.
HTH,
jim b
[ April 09, 2002: Message edited by: jbash ]
[ April 09, 2002: Message edited by: jbash ]</p>