I had a very similar situation and used a combination of bullhead culling and LMB stocking. So far it appears to have worked very well.
Good luck
Here is an excerpt from a previous post of mine
http://www.pondboss.com/cgi-bin/ubbcgi/ultimatebb.cgi?ubb=get_topic&f=20&t=001862&p=0 "The pond is about 1 acre located in Western New york. When I took ownership water clarity was less than 1 ft and the only fish species present were bullhead, fathead minows, and another species of minnow I can not ID. The recomendation I received from professionals was drain/poison and start fresh with LMB/bluegills. I am sure this would have worked but was not very appealing to me. Instead I removed approx 900 bullhead over 3 years. In June 2004 I added 100 3" LMB. The bass are currently about 9 inches and they spawned this spring. The pond is now clear with about 6 ft of visibility (secchi disk). Fatheads are becoming rare and catching a bullhead is no where near as easy as it used to be."
