That's interesting information, how does that work?
The volatility bots assume that the price will hover around a certain running average. When they see it dip above or below they are programmed to buy/sell accordingly. If you want to unload a very large number of BTC the optimal strategy is to stabilize/inflate the price with a buy wall for a bit (artificially lowering volatility), wait for the buy orders to build up above you, then sell into them. This will cause some slippage, but by putting a sell wall midway through your big sell the volatility bots will trade into it (incorrectly thinking it's just a momentary fluctuation). That way you sell 20K BTC from, say 119 to 117, and another 5K at 118. ...this maximizes your selling revenues.
EDIT: It looks like he placed his sell wall too high and wasn't able to unload the 1800 BTC. So expect a slow 1800 dump in the coming hours (in globs of 300-500).