I want to remove the green/brownish algae on it which seems to be making this digitata strip away. The purple part used to be covered but I used a toothbrush to remove the algae, as it was already just dead skeleton, but the algae by the live polyps I am unsure if to do that, I don't want to damage or kill them with a toothbrush but want to remove the algae. What do I do?