I use a penguin bio wheel 200, and my ammonia. Is .25 ppm, nitrite 5.0 ppm, nitrate 80 ppm I have about 15 ish or more guppies fry in there along with 20 guppies in a 30 gal tank. I use stress coat Proper ph 7.0 tetra easy balance n stability when changing water. N I use API master test kit