"Look at today, when someone other than the Algo Trader wanted to buy, the SP rose to 17 cents. then it immediately went to 15. but none of the new buying went for 15.
So the Algo trader does not have to sell to the market in general, only to himself."

I haven't posted for a while due to personal commitments, but I just thought I would chime in here and answer this statement:

I was able to buy today at 15 cents. My bid was hit 50 separate times from 9:38 to 11:35 AM in 500-share chunks. Then, following this, my bid was hit for an additional 32K shares at the same price.

Hysteria