Roh 2099 was a crossed in-house trade - I'd say a part parcel of a 3000 trade as I can readily see 901 in bit parts at 407 in 10min prior to close. As for algo trading they'd be part of a large parcel which in itself is best way to maximise profit [I'll often break down a sale over several days]. Someone is buying an someone is selling - just hope its all arms length stuff =)