Optimum flow rate through filter.

I have a simple question which I thought would be easy to find the answer
to.

Alas, after thorough searching Usenet and the Web, I cant find the answer
to what I thought would be a "frequently asked question", so here goes...

We are in the middle of completely re-doing our pond, replacing a tiny
little custom-made setup to a large pre-moulded pond thereby quadrupling the
size of our original pond.

The pond is the "Eagle" design from the lotus toughline range with a
capacity of 1725 litres (455 US gallons).
We like to see and hear a lot of water on our waterfall, and we also want
to see oxygen entering the water. We have a substantial pump capable of 6000
litres/hour !(1583 USGals/h)

(The Pump is the Laguna Max-Flo 1500/6000)

We also have a filter (with UV) which is suitable for ponds up to 3000litres
(791 US Gallons)

(It is the Green 2 Clean 3000 by Oasis).

I agree that the pump is way too much to flow through the filter, so I have
fitted a T-piece in the hose from the pump with a controlable tap between
the T-piece and the filter. The other output from the T-piece flows back
in to the pond via waterfall bypassing the filter and tap. This T-piece
principle avoids unnecessary strain on the pump.

I can measure the flow of water through the filter by collecting the water
coming out of the filter in to a measured bucket, timing how long it takes
to fill the bucket.

So, you can guess my question...
What is the optimum rate of water to flow through my filter?
What is the general guideline in coming to your answer?
We have about 15 adult goldfish and about 30 baby-fish

My research has shown conflicting answers.. Some quoting "1 pond-volume of
water every 2 hours", others saying "2 pond-volumes of water every hour"

With my T-piece and tap, it is quick and easy to make my adjustment ;-)

Thanks
Brendan

(1 litre = 0.264 US gallons = 0.220 UK gallons )