I assume you mean if you are growing the lucky bamboo in a water pot. Black algae are a general nuisance in any water tank system where you have excess phosphates. Remove your plant and rinse its roots - try to wash the algae off the roots. Clean the pot and use a scourer. If you can, run it through the dishwasher, as the heat cycle and detergents will remove the algae very effectively. Rinse the post again and return the lucky bamboo and refill with clean water with nutrients added. Check main article for nutrients suggested.