The things that are important when you buy an exsisting pond are as follows.1 find out the max. depth.If it is under 10 ft. then you will have trouble substaining a healthy fish population.2probe the bottom to find the hard pan.This will tell you how much build up is in the bottom of the pond.Find out how old the pond is and divide the yrs. by the ft. of sludge.this will give you a good idea of how long this pond is going to last before it needs rebuilt or dredged.3make sure that the spillway or pipe is working without leaks,this can be costly repairs.4check the dam for leaks or is constructed properly.make sure theres not alot of growth on the back side this will also cause problems .5 Catch some fish look to see if the fish are healthy.alot of info on this site can tell you what to look for but I hope this gives you a few ideas that you can use.Good luck DOC

Doc