[Dentoid]

Not sure if their are any hair algae eating stars? This sounds like a nutrient problem and/or flow problem. The best way to combat algae is to starve it into nonexistence. That means, lowering your nitrates with water changes, eliminating phosphate from the water using a phosphate removal media, using RO/DI water for water changes and top off and limiting the amont of food you put in the tank. Also, good flow will keep the algae spores from getting a good foothold. 12 gallons is a small volumn of water that requires strict maintenance to keep in good condition.