This same question was posted a while ago and I think the census was to tip what you would leave in a restaurant, 10-15% depending on the service you received. $250 trip would mean $25 on the low end and $37.50 average certainly $40-$50 is not out of the question if you received excellent service. One thing I will tell you is that the better you tip and the more courteous you are to the guide may get you some "free" information on what the fish are doing later.