Hi Freeliner,
I have the same on my 12500ltr pond - as a newbie to koi keeping like yourself you learn by your mistakes, don't get me wrong they do the job but there are a lot of maintenance involved in these filter systems.
Things to watch:-
UV bulbs sit in a testube glass chamber which can leak and fill with water when backflushing causing bulb to fail
Hose connection leaks under pressure so use some plumbers tape to seal and tighten with waterpump pliers
constant clogging - instructions say once a month strip down and clean, but I've found it needs doing every 2 weeks.
I would say these filter would be very good for goldfish ponds but Koi they are just not up to the task.
Goodluck
Darren | 
