Water is a precious resource and is taken for granted. It is used to sustain life of course but also to make the garden grow, to provide a home for fish and other aquatic wildlife.
Water is used to keep us clean, it needs to be hot sometimes and cold other times. It works its best when softened and for drinking purposes filtered water is nowadays very common. Water sterilizers have also come into common use as natural water quality has deteriorated and we all know how bottled water has "taken off"
The following websites are available for more information:

water gardening

water heating

water softening

water filtering

Secrets of Pond Keeping
As in most things the difference between success and failure is knowledge.
In other words knowing the really important bits.
Many people refer to these as Secrets which of ourse they aren't since the systems and techniques are well known even if not widely spread around. It's
the same with water gardening. You don't have to know everything except some things are vital to understand ... these vital factors include:
pumps, biofilters and UV light systems

IMPORTANT Note about FREE calculators below ... go to
Free pond calculators

You're welcome to download my Excel calculators free of charge.
Know how to choose your pond pump correctly.
You can save a lot of money on electricity by using 2 pumps in a garden fish pond ... a small one to run the biofilter 24/7 and a larger one for a waterfall which can be used as and when required.
If you only have a single large pump then it must run 24/7 to keep the biofilter bugs alive and this wastes lots of unnecessary power (who's there to admire the waterfall while you're sleeping or at work?)
One of the calculators you can download will show you how much money you can save.

Run 2 pumps and save money
As I've said many times .... a large number of retailers do not understand a water pump's specification requirements well enough to give money saving advice consistent with correct water pump performance. Selecting a simple water fountain pump is easier than selecting waterfall or pond pumps.
For a pond you will generally want to select a submersible pump and not one that sits outside the pond itself.
Every Fish Pond Needs A Biofilter
You can learn a lot about the need and understanding behind a biofilter by checking my biofilter site
... so all I want to say here are 2 things ...
You MUST have a biofilter even if you make one yourself if you keep fish in a garden pond ... end of story
Physical size is not important ... BUT the media inside a biofilter is and that's why I recommend the filters and suppliers I do. Most filters are sold on the principle of "the bigger the box the the better (and of course more expensive) the filter must be".
This is NOT TRUE. To select the right filter you need to know your pond volume so get another of my calculators by clicking here
Biofilters for big ponds ...
For ponds greater than about 5,000 gallons I recommend serious equipment that does a seriously good job without lots of cleaning hassles. Do yourself a favor if you're contemplating a big pond and have a discussion with a reliable vendor for these large items ... speak to Brett Fogle (if you live in USA) get large koi pond filters advice here:

Aquabead large pond filters

Your Fish Pond Will Go Green and Murky This Summer If you Do Not Have an UV
Murky green or brown ponds especially in Summer are caused by suspended algae coming to the pond surface to gather as much light as possible (algae are plants and need sunlight to breathe and multiply). This means you will not be able to see deeper than about 2 inches from the surface and this is not the idea behind having a pond in the first place. The solution is simple and guaranteed to work every time if you install an UV clarifier, UV sterilizer or any other name given to these miracle workers.
You can install a combo biofilter + UV and this is normally easiest and best solution ... and they do not cost an arm and a leg.

Learn about Tony Roocroft's downloadable best-selling water gardening books ...
The
Complete Pond Solver
You will find a link on this page to go to the store if you wish to buy a book.

SPECIAL OFFER FOR NEW SUBSCRIBERS
Get 25% ($4.25)off my book "The Complete Pond Solver"
To make use of this offer you will need to use the following Coupon Code at checkout.
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Learn all about water gardens and pond keeping here.

Most pond plants with submerged leaves produce  considerable oxygen
during the day.

Oxygenator Plants. Water Garden essentials ... .. source is Peter J May. For more information on all other types of aquatic plants visit Garden pond plants

OXYGENATORS .... THE ESSENTIAL INGREDIENT

A pool or a pond in a natural wild state is a self-sustaining little world. As in our bigger world, the inhabitants need oxygen to survive. This can be provided by plants growing in that world. If you want to have a naturally balanced pool that requires the minimum of fuss and maintenance, without having to oxygenate the water mechanically, then plants that release oxygen into the water (i.e. oxygenators) are the essential ingredient.

BIT OF BIOLOGY

All plants, apart from parasitic ones, from single celled algae to Baobab
trees, produce oxygen during a process called photosynthesis. This is a
reaction in the leaves (if it has them) by the green chloroplasts of the
plant cells, that uses sunlight or ultra violet light and carbon to create
carbohydrates and sugars used as the building blocks of the plant. The
carbon used is from carbon dioxide, which is taken from the immediate
environment. One of the by-products given off in the process is the oxygen
from CO2. This two-way exchange of gases is called transpiration.

The
oxygen is lapped up by the animal inhabitants great and small of that
environment. But in a pool or pond, it is just as gratefully received by the
(aerobic) bacteria in the bottom of the pond, or perhaps in your case a
filtration system, to aid them in the process of breaking down organic
matter to its constituent chemical parts. It is important to consider some
of the compounds (like nitrates) produced by the bacterial action, will be
used by the plants in the pond environment to boost the growth activated by
the photosynthesis. And if there are not oxygenators and other higher plants
there to use them up, then algae will. The result will then be green water
as the algae proliferate. You see oxygenators are essential, unless you have
a fountain, waterfall, air block or venturi to do the necessary instead.

BUT.... it must be pointed out that oxygenators do not work a 24 hour day.
'When the lights go out', oxygen ceases to be produced and plants join the
queue for the demand for oxygen. So in a very heavily stocked pool that is
overloaded with underwater plant life, resources can be somewhat stretched.

ON THE OTHER HAND... If you keep within the certain prescribed limits then
everything should swing along nicely. Allow yourself only 2ins of fish per
square of pool surface area (or 50cm for every square metre) in a pool
established with 2 bunches for every square foot (20 for every square
metre)... that is unless you keep KOI carp.

In the latter circumstance,
unless you want to give your fish a good feed, keep them well apart. In
certain Koi pools in the past I have found it convenient to have a planting
of oxygenators in the header pool to a stream, which seemed very effective.
They work like filter brushes, slowing down the flow of sediment that even
manages to bypass the filter system. The only problem was that they needed
to be regularly replenished when the header pool had to be cleaned out, (no
problem, see article replanting oxygenators).

THE GOOD AND THE BAD...
Oxygen dissolves from oxygenators into the water more effectively than by
mechanical turbulence

because it is in fact very difficult to dissolve
oxygen into water. It needs to be done slowly and over a large surface area.

All plants that live happily under water can be described as oxygenators.
Out of these plants there are bound to be

one or two that are the best
for the job we need them to do. There is no doubt they are specialised.
Roots tend to be merely for anchorage and the nutrition absorption and
gaseous exchange occurs on the surface of the plant directly to each cell.
The plant therefore has very thin walls and thin leaves to allow this to
happen. This makes the plants floppy, which in fact becomes an advantage
under water as they are able to bend with the eddies in the water. Two
plants that have made this a real speciality and thrive in streams are Water
Crowfoot, the true Water Buttercup (Ranunculus aquatalis) and Curly Pond
Weed (Potamageton crispus).

THE BEST by far for the pool or pond is also
often referred to as "Curly Pond Weed" but is most rightly called
aragasiphon major or more commonly Elodea crispa( South African native).
This has a tendency to take advantage of highly nutritious pond environments
by filling them up, but at least you don't get algae. It is easy control by
just snapping handfuls of it near to the source of growth. Fish love to
spawn on or near it and it is dense enough to provide protection for the
eggs and the subsequent fry.

For conservation and wildlife gardeners it
is not entirely kosher since it is not a native plant. For indigenous plants
to the UK: Water Starwort, (Callatriche stagnalis), rampant but easy to crop
to its source. Water Milfoil, (Myriophyllum spicatum), loves limey pools
with high pH and does well where Elodea crispa fails. You get the bonus of
little flowers in some years that looks magical in certain lights. Hornwort,
(Ceratophyllum demersum), this is often confused with

Milfoil out of the water, but it feels much stiffer and has more forked
growth habit. This is one that does not mind a bit of shade on the pool.

Water Violet (Hottonia palustris), class act for the connoisseur; it has
pretty little pink flowers above the water surface in May and June.

THE
WORST....... The worst thing about some oxygenating plant is not that they
are useless at their job, but that they are very often confused with the
best, or they are sold as marginal plants and quickly run rampant
particularly in clay-lined ponds and then are impossible to eradicate.

Canadian pondweed (Elodea Canadensis), also known as Anacharis, can easily
be confused with the weaker growth of Laragasiphon major. It will even grow
on the surface of marginal plant baskets.

Parrots Feather, (Myriophyllum
proserpinacoides) this is causing some consternation in the States in areas
where the frosts are not stiff enough to knock it back. Sold as a marginal
here, it has submerged and surface foliage and will leap from one side of a
small to another in less than a season.

Mares tail (Hippurus vulgaris),
often sold as a marginal. This plant has been around since time began, so it
is not without a trick or two up its stem!