Well I'd say you what you're gonna do is spend most of the summer cleaning it out lol!!!! But you are dead right, you can't look a gift horse in the mouth!
The idea of having one pond flowing into the other is great but you need to bear in mind the changes in water levels when you turn the pumps off as the extra water flowing out of the top pond will raise the level of the lower one. It works best if the top pond is much smaller than the bottom one. There's also lots of problems with spreading and treating diseases between koi and goldfish so personally I'd keep them separate. You could always cheat and make them looked linked by a bit of clever landscaping with a waterfall and bridge or something similar.
A raised koi pond is a goo idea IMHO anyway as it brings the koi up and reduces the amount of dirt blowing into the pond which then needs to be removed. My next one will be a raised streamflow design but that's another story!
Thanks Ed, it's a good point about the overflow of the two ponds, kinda like a sump i suppose.
Id be interested in how often i need to clean the filter out, currently the FishMate 10000 needs cleaning every week, if i forget, it clogs and water billows over the top and empties my pond overnight, this has happened twice now! A change was in order. A K1 bad boy is still the order of the day, it may have to wait till next year or the winter.
I think i've sorted a pondvac so thats a bonus
I went out to feed the fish last night and my god, the pond is so clear it's untrue, it's not been that clear since the day i filled it. I can see right to the bottom, which is annoying since you can now see all my crappy pipe-work
I haven't drained the filter off yet but it's supposed to be easy, we'll see!
I'm looking forward to the pond vac, now that it's clear i can see all the stuff i need to clean out. It'll be a dirty job