As the user above said pretty much, also worth taking your sample to an aquarium and get them to check it for you to see if the results are near your readings. Add some Bactria to the tank and ensure you add lots of plants. Fish poops then the poop turns to ammonia, then the Bactria eats the ammonia the turns to new nitrite then Bactria eats that with some getting absorb in plants then the Bactria converts it to less harmful nitrate which will be all absorbed into the plants