Two things:
* Rinse your polypad filter regularly, every few days to start with, and replace it every week or two. That filter is a great source of trapped organics that will convert to nitrates. Rinsing removes the organics. Some organics can't be rinsed out and replacing the pad removes them.
* I think a lot of the confusion and argument in this thread is because people are using the term 'bioballs' when they really mean wet-n-dry (or trickle) filter. It's not so much the bioballs themselves, it's the highly oxygenated process of that filter.
I also think that proponents of wet-n-dry who work in LFS are confusing the very different requirements of a LFS with a home aquarium. In an LFS, the main object is to avoid poisoning the water of very heavily stocked tanks, and wet-n-dry are terrific at converting large amount of toxic ammonia to 'harmless' nitrate. At home, we don't have anything like that bioload and our aim is to be a bit more refined: we want to push the conversion process all the way through the anaerobic stage of nitrate to nitrogen.
My own opinion? Try rinsing the pads for a few weeks and see if the nitrates stay low after some water changes. My trickle system had nitrates around 20ppm and they reduced to less than 10ppm from that alone. I ended up removing the bioballs completely a few months later, effectively converting the trickle filter system to just being a sump, and the nitrates are undetectable, prob around 1-2ppm.
