For most varieties of algae, you’ll need to feed something nitrogen based with plenty of phosphorus, but there are a few varieties out there where sugar may be required for optimal growth. These would be the algae that don’t rely on photosynthesis in order to produce food. Usually, these are specialized varieties meant for use in bioreactors or other niche applications like pharmaceutical production ore research.
Using sugars as a food source can be quite expensive, which is why the production of these types of algae isn’t as common as the production of photosynthetic algae. This is compounded by the fact that in systems relying on sugars as the food source, there may be extra maintenance required since secondary biofilms often form on equipment like pumps and circulation devices, which can lead to the contamination of the algae culture.