Moving Bed Filter

Anyone have and ideas regarding moving bed filters.

I've seen some DIY versions on the net and I reckon I could make a small one (1/2 litre bottle for hospital tank)

a)     Are they any good

b)     Are Hel X really any good or would something like Bio motion balls be better

c)      Do Gel Bacteria starter balls really help

d)      If none of the above what sort of filter should I look at for my little hospital tank please

I agree with NM and don't know too much about moving bed filters.

With regards to bacterial balls, I was skeptical until I read this article (http://www.practicalfishkeeping.co.uk/content.php?sid=4918). I used Pure Aquarium balls when adding fish to my cycled tank and NH3 and NO2 remained at 0 throughout. I've seen several posts by people who've used them in QT tanks when they haven't had a filter ready to go and they swear by them.