I remember when carbon dosing was the latest craze, and people were adding vinegar, vodka, ethanol, sugar to their tanks. There were many tank crashes, biofilm takeover, huge pH drops, and oxygen depletion.
Yes, adding too much carbon will cause a bacterial bloom, but with today's technology of dosing pumps and controllers, I believe it can be effectively controlled and ultimately dialed in. We shall see when I find a reactor. But that may be far down the line as it'll only be needed when there is a large bioload...which to me...still seems very very far away for me.