From this question I think you need to spend some time reading the thread. It has all that information in it. I posted a really cheap option that works great
Here are some little details I pulled out from the thread looking back over a little bit of info for you. Enjoy
What does a Reactor do for NITRATES?? This is not a nitrate remover, this is about helping waste cycle better and more efficiently
Water changes is the nitrate remover in an aquarium setup. This is for growing good Bio and the most active is young Bio to cycle all the food thrown in the tank from ammonia to nitrates, just like other Bio filtration other then this is growing young Bio and shedding the old for best opportunity to have young healthy Bio growth all the time to be the most effective at eating and converting bio mass left behind by left over food or waste.