You could try putting the roots of a house plant into the tank which would use the Nitrate. I have read about people using Epipremnum aureum, commonly known as Pothos Ivy. It works well if you have a hang on back filter. I have a Pothos plant at home that I plan on putting in my filter. Just rinse all of the potting soil from the roots. And then only put the roots in the tank or filter. Then most people use some string and nails to attach the plant to the wall.