Well, here goes:
The perfect pond plumbing system would include:
1. A bottom drain. But NOT for feeding the biofilter. This is because biofilters are best fed
clean water not loaded with lots of organic solids that will clog and render them inoperative.
Bottom drains are perfect for draining bottom mulm to waste. This is much easier if you have a
topography that would allow this to be done by gravity flow, but a standpipe and refuse handling
pump will suffice. Generally a weekly five minute open bottom drain will keep bottom mulm to
a minimum. Of course the pond would have to slope toward the bottom drain(s) to be effective.
2. A skimmer. This is important in the spring, summer, and fall to keep the water surface clear
of pollen, tree seeds and other flotsam that blows into the pond. The skimmer should be
equipped with a pre-strainer to keep trash out of the biofilter.
3. A side drain. The side drain, equipped with a strainer to keep out fish and trash is the best
source for most of the water going to the biofilter, since it will be the cleanest source in the
pond. Side drains should be situated about one half the pond depth. In climates where the
surface freezes, skimmers become ice jammed, and if you keep your filter system running year
round as I do*, the side drain keeps the water flowing without disturbing or super cooling the
bottom water where the fish are likely to congregate.
*Yes, I know all the jabber about biofilters not being operative in cold temperatures. But by
running the system 24/7/365 there is no guesswork about when to turn off or when to start up,
which if miscalculated, can be hard on the livestock. Also, by keeping the pumps running, I
don't have to drain everything or worry about frozen pipes, at least in my climate. You DO have
to engineer your return so that an ice dam will not result in a partially empty pond. (Remember,
by NOT using the bottom drain to feed the filter system, you will never completely empty the
pond.) Note: For those using submerged pumps in their ponds: Place your pump at one half the
depth of the pond and you will also avoid the "empty pond syndrome".
4. Adequete pipe size. Be sure to provide pipes large enough to provide the flow you require.
if you need help figuring pipe sizes, see my webpapge at
http://www.gardenendeavors.com/rack/pool10.htmlIf you only want to determine pipe size requirements for a given flow, simply enter pool
dimensions in the calculator that will produce a flow close to what you want. At the bottom of
the page is a link to my head loss calculator, which will help you select a pump with sufficient
head for your pond.
Most of my ideas about how to accomplish creating a pond are at my page
http://www.gardenendeavors.com/rack/web2.htmlBy the way, Esther's comments above are very good. pay close attention to them.
Regarding "always build the biggest pond you can": I have always given that advice, because
just about everyone I have ever known that built a pond has said they wish they had made it
larger. This is because they want more fish and more plants and just the enjoyment of a larger
pond. But, there is something to be said for starting small. Ponding is a learning activity.
Progressing from a smll pond to an intermediate one then to more ponds or a bigger pond will
provide opportunities to enjoy the experience of discovery and learning for oneself what you
like and dislike about various ideas you have tried. In the long run, it might be better to make
small mistakes than one big one.