All I use mine for is to move water around. I don't like the bio-balls or whatever you want to call them because they collect a lot of detritus. I had a tank up and running for a while and thought everything was going swimmingly. One day I noticed that I was begining to get high nitrite reading and could for the life of me fiquer out where it was comming from. It took me a couple of weeks to figure out that it was coming out of my filter. I took out the media and problem solved.
Hope this helps
Chris