[MCA]

I can see I will have more research to do.
Do the TT need to be a certain diameter?

MCA: the larger the pipe (anywhere in the system) the less resistance to flow. Most folks have done pond returns (to TPRs or other) via 1.5" or 2" pipe. Again 2" gives much less backpressure on the pump (a good thing). Use a ballvalve on the output of the pump to control flow...not pipe size restrictions. To me TPRs are grossly overrated....if you run air domes 24/7. I have yet to see a TPR that makes an detectable horizonal rotation compared to the huge ring/donut currents caused by air domes. To me, TPRs are OK...but not a really an effective way to move lots of water.


What do you think the shortest vetical height I could get away with is?

MCA: A pond can't be too deep for koi (riverine carp). They need all the room (vertical is just as important as horizontal) we can give them. Our pond is 8'...2' up and 6' down. Given a choice, I would never do a koi pond with less depth. To me 6' should be the minimum target depth. Again, read those books on the list!!! Remember, you are dealing with large riverine carp, not small goldfish. There is a huge difference in what makes a good environment for those two different fish species.


I have in my plans to use a small Tea House to help disguise the filtration system.


MCA: The tea house idea is fine. You may have conflict when the word small gets involved. Filters are not small. You need room to move around and open/close valves, flip switches, change lamps...etc. But we are getting way ahead of ourselves. First do the preliminary pond system research with the books, local club members, and crazies on the BBSs.