Hi Terry,
DWC refers to deep water culture. Looking at your system, it looks like a flood drain, so DWC issues wouldn't apply.
When I built my swirl filter, I tried to avoid those bottles with the handles since it seemed like they wouldn't swirl as well. I wonder if that's been the case for you? You can get a round one
here or at your local brewery store.
I'm currently looking into developing my filter system further to take out more of those particles, experimenting with bird netting and such. I know UVI uses tilapia in their swirl filter to clean the walls.