This is what I came up with. There is a a BIO bag from my old filter in the top. I was going to use BIO balls but the soda caps were readily available and I figured they would work the same. Its a bit loud but, I think I can fix that with a few more holes in the top. Let me know if you think this will work as a second filter.
Video here: (ignore my 2 year old yelling "I win" in the background!)
Video here: (ignore my 2 year old yelling "I win" in the background!)