What plant do you have? If you hade just one plant and a sufficient plant light that will also help feed algae. What kind of light do you have? If you have a sufficient light I would get some more plants.
One thing to keep in mind is if you have a plant light and nutrients in water which you will just from fish waste, nitrates, etc then that will feed the algae. The more plants the less nutrients the algae will get because the plants will always get the nutrients first.
But it takes very little for algae to thrive. Very little nutrients, very little light. So if the plant or plants are lacking say with light or nutrients or both or there is too much nitrates or too much ammonia then algae will win. Give the plants what they need to thrive with right balance of nutrients and light then the plants will thrive and algae will not.