I just got a nitrate tester kit and found out that my 48 gal. has about 7-8
mg/L of nitrates. Is that getting pretty low for plants? My 15 gal. has
absolutely no traceable amounts of nitrates...this means that all the
available nitrogen is being used and that possibly some are starving for
nitrogen. What can I do to add more nitrates into the system?

THANX!!!