I admit to using Flourish Nitrogen, and in much more water tha 20 gallons. But i am not doing high light/high CO2 either. If I need to add N to a tank or to the range, the Seachm product is convenient and fairly stable, althoigh more costly than dry powder. But it is easier for me to use and miles more convenient - for which I am willing to pay.
Personal choice item, your tank, your choice.