Question
i have a pond 9"long by 4" wide the deep end is 4" the middle 3" and the shallow 2" deep in it i have 13 fish 4of which are ghost koi 5 gold fish 2 shurbunkins and 2 comets all doing really well how deep and big should it really be to hold this many fish the water is clear and i always do a ph test ive got three water pumps running in all three depths thankyou

Answer
From my approximation, I believe your pond is between 700 and 900 gallons.  The very conservative estimate of gallons per fish is 500.  That is 500 gallons for every 1 adult koi.  What you have is not too bad, and certainly not the worst I've seen/heard of.  I would personally want about 2,000 gallons for that amount of fish, although many others would say that 2,000 gallons is a little shy of the desired mark.

The true test is to see how the pond handles ammonia and nitrates.  If you rarely see any concentration of ammonia and the nitrates seem to dissipate before building up past approximately 60ppm (plants use nitrates to grow) then your fish should be fine.  If you don't have plants (or enough plants) you may need to perform small, regular water changes to keep everything healthy.