Is there any truth at all in a 1000 gallon closed loop bio-pond for
Koi??

Sure, absolutely possible! In fact, it's just like this highly successful
closed-loop scheme described below:

Glorious Opportunity To Get Rich!!! -- We are starting a cat ranch in Lacon
with 100,000 cats. Each cat will average 12 kittens a year. The cat skins
will sell for 30 cents each. One hundred men can skin 5,000 cats a day. We
figure a daily net profit of over $10,000. Now what shall we feed the cats?
We will start a rat farm next door with 1,000,000 rats. The rats breed 12
times faster than the cats. So we will have four rats to feed each day to
each cat. Now what shall we feed the rats? We will feed the rats the
carcasses of the cats after they have been skinned. Now Get This! We feed
the rats to the cats and the cats to the rats and get the cat skins for
nothing!

There are apparently a lotta people around with more money than brains. But
at least it's his money - it ought to cost a not-so-small fortune to build
an all-granite pond, even if it's only 1000 gallons - which is about right
for ONE Koi! I say, tell him to go for it, who wants to listen to all these
know-it-all porgs on rec.ponds!

Happy Ponding,
Tim
900 gallon open-loop goldfish pond