Regarding division of pump flow: actually, the division of flow really depends on resistance and back pressure. For example, I used a 20 gal small garbage can as a Skippy Filter and intended to split the flow 50:50 to that skippy and the rest to another portion of a stream. It turned out that the skippy lines were so resistant that 3/4 of flow went the other way and I had put a ball cock on the skippy line which didn't need any attenuation.

If you wanted to control your splits, I think I would put ball cocks on all lines so that you could set controls as needed. However, I suspect you would be happier not fooling with bottom cleaning and let the stuff build up out of the way. You might want to google or just search here for cliffandjoann and filter to see if their detailed pump filter system would help. Their pond is much bigger, but I suspect that your filter system is too fine, too small, and will be a big pia and other than the skimmer, you might want to fill it with a media catching deal like sponges or something else like a skippy uses.

Of course, I have never convinced myself of the usefulness of my Skippy. I have a big stream filled with plants and great gobs of plant roots that I believe do most if not all my filtering. The Skippy probably does do some biochemical activity, but at least many years ago now, I removed the skippy looking for a leak, and found it to be almost clean of any thing obvious. Now, the sponges etc all seem loaded to the gills with muddy stuff, so I suppose it is really doing something.

Aha - good info about the division of pump flow. Makes sense the pumped water would take the path of least resistance.

Found the info on cliff & joann's - wow : http://forums2.gardenweb.com/discussions/1577752/our-pond-maintenance-and-set-up?n=18

HMMMM BOTTOM DRAIN - that's a whole nother concept - I don't have one but do see that there are ways of retrofitting....?

Is that what you mean by "not fooling with bottom cleaning" - having it pulled out and dealt with elsewhere? I have to have some circulation down there, and not just an air pump but something that actually moves the water around. My pond is kinda deep in relation to its size.

If I have the pumps in the exterior tank, how do I calculate the size/power of the pump I need? Is it same as if the pump was at bottom of the pond (figuring in head height, fittings, length of tubing etc.)

To be honest, I was playing both ideas against each other. I gave you the cliffandjoann for their detailed approach to aggressive filtration because I am assuming your system is too small and perhaps using too fine filters besides (and I'm too lazy to recheck their site myself). I was thinking that you could use their approach with an in pond bottom pick up instead of stirring things up to grab the crud. It still uses flow from two places (just different directions).

However, I was actually suggesting that instead you could go the other way and do nothing and just let some crud build up on a semi undisturbed bottom and if you get ambitious, you could yearly or decadely drain and scrape/suck up the crud and start over with new water.

I love looking at C&Js pond pics and videos. As long as the 'pool boy' keeps in shape cleaning those filters, I am happy to watch, but I think I'm too lazy to build or keep up with that.

I think the pump calcs are based on height and pipe resistance like you said, and I assume c&j probably covered that and filter issues too somewhere.