That's interesting to know. I was told that nitrite is not really an issue until the 1st stage of cycling is complete, that is, when ammonia goes down to Zero.
If plants can do this with ammonia, imagine what they can do with nitrites & nitrates
Scenario 1) No nitirtes have developed because the plants are using almost all the ammonia for themselves...This could significantly prolong your cycling.
You should of had some nitrites present by now...
Scenario 2) You may have a cycled tank and their are NitrATES present, that are converting toxic nitrITE to a safer form. Unless you test, you wont know...Plants do little to lower nitrite/nitrates if anything at all, so i tend to go with scenario one, your tank has not yet started to cycle...
What this means is, you must be extremely cautious with adding any stock...Without the nitrates present, it could cause a viscious ammo spike and kill your tank off...If you do go to add more, do so slowly...Perhaps one fish every 10 days or so until the nitrites/nitates start to take hold.