A Small peristaltic pump such as the P1 or P1 Pro can be used. These pumps are able of dosing small ammounts at programmable intervalls. Once the total ammount of the fluid needed per day is known you can set the pump up to add this total quantity divided in to small doses throughout the day. This way the bacteria have a near constant available carbon source that can be fine tuned depending on the needs of the reactor or the nitrate level in the aquarium.