Check your nitrate and phosphate, first thing to see if its elevated. An excess of available nutrients, particular the majors like phosphates and nitrates contribute to this. Keep an eye on possible iron and potassium sources which may also help fuel hair algae. Hair algae spores and fragments are so abundant that keeping it out of the tank via quarantine is unlikely to be successful. Your best bet to preventing this algae from taking hold is to maintain a weekly water change regimen, maintain your filtration and perform manual/natural algae removal as it forms. Proper magnesium and alkalinity levels are thought to discourage the growth of many species of GHA.
Green Hair Algae or GHA is really a broad term that covers hundreds of species of green simple filamentous algae. These species tend to be simple, fine in texture, and have few distinguishable features. True species level identification requires a microscope. GHA is not coarse or wiry, it should break apart easily when pulled, and should lose form quickly when removed from water. If you can make out a root structure, or a stiff branching structure it is probably not GHA.
Green hair algae can be pulled out easily, and tooth brushed or scrubbed off the rock work. This is easier to do if the rock is outside of the tank. If it is growing from the sand sift it out with a net.
Lastly- add some helpers such as Blue Leg hermits, Cerith snails, Chitons, Turbo grazers, Sea Hare, Conchs, Emerald Crabs, Urchins and astrea snails.
