Ok this is highly unlikely but just is simple super duper easy thought that wasn't mentioned and I didn't see posted.

You said you changed your filter 2 days prior to pouring in the bio-d. The bio-d would have losend a lot of crap and put it through your filter (could be plugged already even after 2 days) Except you said your tank screen was clean soooooo not sure of the chances of that. But like a said a super duper easy place to start is always filters.

Does is slow over time or is it right after starting it as well?

__________________
76 300D 130K "Stella" (Sold )
74 240D 299K (Donated to Highschool For Senior Project WVO)
83 300TDT 290K (My one and only)
Sanford, NC