The pond you have is beautiful and sounds like you know what you are doing. Since you already built one you know the problem areas and what you woud change if you do it again. A suggestion would be to use a media other than lava rock. When used without a really good prefilter it will collect poop and hold it requiring you to remove and wash the rock. If you go with a fluidized filter it will have exponentially more well oxygenated surface area and is fairly easy to back flush for cleaning. Here are some ideas
http://www.koiphen.com/forums/showthread.php?t=47375
http://www.koiphen.com/forums/showthread.php?t=68339&highlight=birdmans
Poly strapping is another cheap effective media. It can be stuffed into pretty much any chamber with flow through it. On the bottom of the chamber run a grid of perforated piping. When its time to clean attach a shop vac on blow, or spa blower, and the rush of air knocks all of the poop off and out the waste drain.
Here is one I am building with strapping in it, but you could probably use lava rock if you wanted to.
http://www.koiphen.com/forums/showthread.php?t=69030&highlight=birdmans
http://www.koiphen.com/forums/showthread.php?t=47375
http://www.koiphen.com/forums/showthread.php?t=68339&highlight=birdmans
Poly strapping is another cheap effective media. It can be stuffed into pretty much any chamber with flow through it. On the bottom of the chamber run a grid of perforated piping. When its time to clean attach a shop vac on blow, or spa blower, and the rush of air knocks all of the poop off and out the waste drain.
Here is one I am building with strapping in it, but you could probably use lava rock if you wanted to.
http://www.koiphen.com/forums/showthread.php?t=69030&highlight=birdmans