Kingsland:
I would also not treat the main tank if it's not showing any signs of the problem hair algae (appears to be a derbesia sp., from what I can see, but it's almost impossible to positively ID). What a great frag tank, btw. I find it interesting that the hair algae appears to be starting at the bottom of the plugs.
I also had a bloom of brown hair algae (kind of looked like small tufts of brown cotton candy) on my frag tank's eggcrate. Algaefix took care of that quite easily. In fact in my case it was much more effective on that than on the longer green hair algae.
In any case, here is a suggestion: Place a saturated solution of kalkwasser in a shallow pan or dish. Then, one at a time, place the frag plugs upright into the pan, making sure that the coral itself is not allowed to contact the solution. Ideally, all your frag plugs will be identical, and the depth of the kalkwasser can be such that only the stem of the plug and the underside of the plug face can be in contact with the solution. Keep the frag there for 1 to 2 minutes (as long as you think the frag can stand to be out of the water). Then place the frag back in the tank. The high pH and caustic nature of the kalk will cause the algal cells to burst and die almost immediately.
I have used this method many times on both frags and items like return pipes and powerheads. It adds nothing harmful or undesirable to the water and is very effective wherever it comes into contact. It may give you the upper hand against the pest and allow the Algaefix to attack what's left. You could also remove the frags from the racks and treat the bare racks outside the tank the same way. With kalkwasser about as cheap as dirt and basically harmless once diluted in the tank water, I find this a means of attack impossible to accomplish by scraping or other means.
