I take it your system will be pump feed as opposed to gravity, ie. no bottom drain.
If I were in your shoes, I'd go for a bottom drain. I have just built a 3000gl pond and was saying to hubby just the other day, thank GOD! we put in a bottom drain, it makes filteration sooooo much easier. Don't forget Koi are dirty fish that create a lot of mess, there's no such thing as a self cleaning filter, even with the nexus you've got to flush it once a week!!
Have a good look at this website, especially the construction bit, I'm glad I did
Good luck
Posted on May 5, 2005, 5:07 PM from IP address 80.176.91.232