My 10g community had 0 nitrates. There were TONS of plants in there. Rotala rotundifolia, dwarf green hygro, wisteria, java fern, rose sword, java moss, amazon frogbit, and duckweed.
So, are the plants that you have in the filter terrestrial?
100g Native Fish Pond, 55g Goldfish/Catfish Community, 50g Plant Pond, 40gB Tetra/Cory Community, 20gHM Community, 20gH Turtle (Bender [RES]), 20gL Turtle (Kif [YBS]), 15g Reef, 5.5g Betta (Okami), 5gFBH Betta (Pron), 5gHex Betta (Twister)
2 dogs, 13 cats, 2 turtles, 1 bearded dragon and 1 crested gecko