an almost never used concrete w/ plaster swimming pool. It was built
in 1989 and is 18,500 gal, kidney shaped 16'x32'. As a diving pool the
deepest section is about 10' and slopes from about 3'. Naturally I am
thinking I could turn this into a pond since the hole and plumbing are
already there. The 10' depth seems a little much for a pond and would
make maintinance somewhat of a chore.

I have a concrete, stone and mortar swimming pool that I made into a
pond and I love it. I filled in the pond to a depth of 3' to 4'. That
way I can use waders for maintenance. My pond is spring fed, so I don't
need a filter system.

I wanted lots of plants, so I got plastic nursery benches that are 2' by
8' and placed them around the edge of the pond. I keep the benches
covered with marginal plants.

Our pond is 18,000 gallon (17'x 47'x 2-4') and is spring fed. It filled
up in 2 days so the flow is good. The spring water's temperature is 50
F. The pond's temperature gets up to 70 F by the middle of summer.
When first filled with water, it quickly covered over with string algae.
I put 12 trap-door snails in the pond and they multiplied at a fantastic
rate. Soon they were eating the string algae. Frogs came into the pool
at an alarming rate. Marginal plants are doing very well. The water is
reasonably clear. Algae is caused by nutrients in the water and
sunlight. Here is what I do:

o Planted 10 water lilies and one lotus, which have large leaves that
shade the pond surface. Shade is important in preventing algae. I let
Azolla caroliniana ("Fairy Moss") cover the surface during the winter
and early spring to provide shade before the lilies and lotus form their
leaves. Then I scoop most of the Azolla out with a swimming pool
skimmer net so I can see the fish. It doesn't come back until the next
winter.

o Planted about 64 marginal filter plants in baskets with clay soil
(Walmart's cheapest Kitty Litter) and no fertilizer around the edge on
the 8' plastic greenhouse benches about 5 inches below the water
surface. Marginal plants remove nutrients from the water and prevent
algae.

o Introduced trap-door snails into the pond which eat dead material in
the pond and hence break down plant nutrients. The snails multiply
nicely each spring and take care of dead plant material.

o Sunk oxygenator plants on the bottom, Anacharis and Hornwort. I also
have a 1.7 CFM, 40 Watt air pump and two aerator heads to keep the
oxygen levels up in the winter when the plants become dormant. The
higher oxygen level helps support fish and aerobic bacteria. Adding the
aeration changed the water from a tea color to a more clear color.

o Floated a bale of barley straw near the spring pipe. This helps
prevent algae when it blooms in the spring before the marginal plants
get going.

o Introduced 100 native golden shiner minnows. They help keep mosquito
eggs and the plants in check and don't seem to add to the nutrient load
too much. They are doing very well and have multiplied.

o Apply one dose of algaecide (AlgaeFix) in early April to get a start
in clearing the spring algae growth.

o Added bacteria (Microbe-Lift Spring/Summer) in early April to help
eliminate the dead algae and other organic matter.

No filter, no UV, no water pump, no Koi, no problem.

I am in zone 6 and get a lot of hot weather in the summer.

For a view of our lily pond visit:
http://home.dejazzd.com/shenning/pool8-18.jpg
--
Pardon my spam deterrent; send email to
18,000 gallon (17'x 47'x 2-4') lily pond garden in Zone 6
Cheers, Steve Henning in Reading, PA USA