There is and I think always will be world wide controversy over carbon being used in a planted aquarium. There still is no “factual scientific evidence” that carbon either strips nutrients from the water and also no evidence that it leaches its waste products back into the water column. I do use carbon in my planted tanks and find nothing wrong with doing so. Plants are healthy and have good growth and also very little algae present in either of my tanks. Below is a table of what carbon is supposed to remove from the water column and as you can see by it the only source of nutrients it removes is potassium, which is good to moderate. Potassium is a nutrient that plants need but not in any great amounts. The main problem with potassium removal will probably show with leaves getting holes in them. If this does happen then simply increase potassium dosing or remove the carbon.