Well, I am planning a total of 6 ponds.  (You’re not the first one to think I am crazy)  
     I will start to explain myself by starting with where the water will come into the system, and continue with the story until the water leaves the system.  Since I am on city water, the water will come in off the main  line.and enter what I am calling a "conditioning pond".                    
    This  pond will hold about 2000 gallons of water.   It will hold the water and age it so the water is safer for the fish when it does enter the ponds with fish in it.    I would like this pond to be at the top of my lot.   My lot slopes from the back of my lot to my house.  It will be in the Feng shui   section of relationships of my place.   So,  I am going to build it in a heart shape.    For a fountain I am planning on having two of those statues from Brussels of the little boy peeing.   I think having two of those standing side by side gives a tender innocence to relationships.   It also moves the water so that the chlorine has a chance to evaporate out of the water.    This pond will have no filtration except a leaf basket.  It is for only aging the city water making it safe for the Koi, and will be totally drained twice a week during the partial water changes.  I will explain more about this later. 
     This pond will have a bottom drain which will split and one split will go to the pump box that will host the pump that supplies the urine to the statutes and the other split will gravity feed to the main pond that will have a valve.
     The valve will control the refilling of the main pond and insure that it stays full.  (I have ADD and if it is not automatically it might get missed from time to time)  
    The main pond is going to be 19’x24’ about 6 1/2 deep in the shallow side and 8 feet deep in the center.    Yes it is going to be a big pond!
     I have decided I want  two bottom drains.  The data that I have found states that you should allow each drain to pull no further than 10 feet in any direction.  With it going 24 feet wide that would be impossible to place one drain where the drain would pull water from 10 feet away and have the bottom covered.   So it is my wisdom to place two drains in the pond. They will each be about 7' from the center and from the edge of the pond so I will have good coverage.  
  Now for anyone reading this if you have knowledge or insight please  sign my guest book or email me with comments, and input.   I need lots of feedback.  
 Anyway,   the water will gravity feed through a 4 inch pipe and once outside the pond It will  enter a  vortex tank.  I found these tanks second had from a garden shop that was going out of business.   They are both large,   and the water will  slowly  go through the vortexes to allow the solids plenty of time to drop out.  (A vortex tank is a coned shape tank that allows the water to enter down low and spin and flow up.    The water  moves slow and the solids tend to fall out.  A very good prefilter)   From the vortex tanks the water will flow into home made filter boxes that will have 10 inch long 4 inch diameter brushes the complete the mechanical filtration.   The water will then flow into another filter box which will be my biological filter.  I recently went to the Central Florida Koi Show and while there I purchased a pressurized tank bio filter.   
     I am still building my own biological filter to add to the pressurized bio filter because I do not feel it will be big enough to accommodate the entire pond.    The filter media I am using  in the homemade section is bottle caps.  I work in an office building with about 400 folks.  We drink many bottles of soda and water and I collect as many of these as I can.  I am brining them home and placing them in trash cans full of water.  I have air stones in them and I am pouring ammonia into the water each day.  I have been doing this since Jan, 6, 2008.   the ammonia levels are still a little high in the  water but since I have no fish in them  I am not worried.  I am hoping to "pre-cycle" the filter media and therefore maybe  not  so stressful cycling the pond.  Cause after all it is the filter media that cycles.  We just monitor the   water to check for progress. 
But back to the flow of water.   once the water flows from the biological filter it will flow into a tank that is just for the pumps to pull from.  
     I am planning  in the future to have the water return   through  three smaller ponds with individual  filtering systems that will over flow by  streams and waterfalls into the main pond.  More will come later