High Anxiety External Pump Choices

[Smilingcrafter]

I have read till I am blue in the face & still am at a loss as to what size pump I need.  If I understand correctly Performance Pro. and Sequence are good brands to go with, but I have no idea which one (Size or Model) I need.  Please Help  :'(.
I have a 29' X 17' sort of kidney shaped pond.  The deepest part is about 3.5' deep, but the avg. is about 2.50'.  The waterfall is about 5' tall.  The way it is currently laid out, the external pump will take water from the furtherest point of the pond from the waterfall, and deliver it to a 150 gal. Skippy filter behind the waterfall.  Then the discharge from the filter will disperse down the waterfall which is about 2.5' wide.  I hope I have given you enough information.  I would like to have Koi in the pond, and I need a external pump that is good with energy but I also would like good flow on the waterfall.  Oh, and the bummer is I really have to watch what I spend, but I do not want to sacrifice quality (I might have to save $ for a while ).  I apologize for asking so much of you, but could you also suggest some trustworthy online stores to find the pumps. 
Thank you

[dperry]

The volume of a pond in gallons is calculated by finding the number of cubic feet (length times width times average depth) and multiplying by 7.43 (the number of gallons per cubic foot).  Were your pond rectangular, the volume would be about 7600 gallons.  You want to circulate the volume of your pond at least once per hour, so choose a pump that will move that much water with a head of at least 5 feet.  In reality, to be very accurate, you need to take into consideration the size of the pipes, the length of the pipe and the number of turns in the pipe.  I would look for a pump that can deliver approximately 8000 gallons per hour.  I buy my pond supplies from Foster and Smith  http://www.drsfostersmith.com/   They are reliable and reasonably priced.   http://www.drsfostersmith.com/pond-supplies/pond-water-pump/external-pond-pump/ps/c/5163/5164/9375

[Mike R]

I have a similar sized pond & like you, I read and read lots of posts about necessary equipment.  I 2nd everything in the post above by dperry.  I have a Sequence 7800 pump--in it's 6th year with no issues.  It probably nets about 6000 gal per hour considering the 5 foot rise, 30 ft. of 3" flexible PVC and 2 90 degree turns.  External pumps are a little more expensive at initial purchase but last longer and are easier on the electric bill.  Mine takes about 580 watts.  That translates to about $35 mo on the electric bill.  The sound of the water drowns out the sound of the pump. Lastly, I use filters at both the skimmer end and the waterfall.