If your question is for me then yes. I would turn off your filters and or powerheads to let the water settle, fill the syringe with the amount of excel needed for your size tank, then inject excel directly onto the algae, and repeat every day or every other day on different spots. Don't forget to turn your equipment back on after about 15 to 30 mins.
However now that I think about it if you don't have plants in the tank to use that excel your putting in there then you may run into an overdose problem. If there's an algae problem in the tank then you really need to find out the type of algae you have, it's cause, and other ways to resolve it before going with chemicals.