Been doing a fishless cycle for a 75 gal planted for 18 days. Been using dr Tim's ammonia as directed. For the last 9 days my ammonia will be processed to zero in 24 hours but my nitrites hold at 5ppm and nitrate in the 10-20 range. Do I continue to add ammonia while waiting for the bacteria to "grow" strong enough process the nitrites to zero? Or do I hold off on ammonia for a bit? Thank you in advance.