So with feeder guppies, I advise that you do a 50% water change when either ammonia or nitrites reach 0.50ppm on either test. You should test ammonia and nitrite everyday.
With fishless cycle method, the ammonia is at the set level you add it, like 2ppm, and you just wait. Test nitrite every 2-3 days, until you see it go up. At this point test ammonia, and see how much it goes down. Once ammonia gets to 0ppm, you add more ammonia (up to 2ppm). Watch nitrite level. Once nitrites hit 0ppm, test your nitrates, and it should show above 0ppm. Redose with ammonia up to 2ppm, and if ammonia is 0ppm, and nitrite is 0ppm 2 days after the 3rd dose, you are good to do a large water change to reduce nitrates and add the bichir the same day after the water change.
Test your tap water for ammonia, nitrite, and nitrates so you know what you are starting out with.