The debate continues...

if you are completely washing them out every couple to three days you should be fine.

the reason HO filters are bad is that they are usually left running for months without cleaning. they contain floss of some kind, this traps detritus (which is good) that needs to be removed often in order to keep from becoming a nitrate factory. a naked HO for water flow only or as a container for carbon is fine.

G~

Geoff is right, the filter materiel whether its poly batting, sponge, or what ever does trap debris as well as provide a high oxygen environment that favors the bacteria that excell at breaking down the ammonia and nitrate that results from decomposition, this process results in nitrate production.
The bacteria that break down nitrate favor a low oxygen environment in which to live, which you aren't getting to any extent in a power filter, BUT
hopefully the products you are using do live up to their claims, so you are essentially removing them chemically rather than biologically. As long as the De-nitrate/phosphate contain no chemicals that adversly effect the tank, you should be ok

Shack! How ya doing buddy!? Long time no chat! Left a voice mail for ya bro.