Plants

Marginal Plants - Plants that thrive in consistently moist, boggy soil. e.g. Yellow Flag Iris, Cattail, Pickerelweed, Arum_Arrow.
Surface/Floating Plants - Waterplants with leaves that float on the surface, while roots trail below. e.g. Water Hyacinth
Deep Water - Lily   Hardy (Perennial)   Tropical (Annual)
Oxygenating Plants - these will be completely submerged in the water. e.g. anachris

• Fertilize your plants with plant tabs at least monthly during the growing period.
• Planting Medium:
  - Some sources say to NOT use garden soil or planter mix as a plant medium. se Use special aquatic compost, which is low in nutrients. Flourite and Onyx are specially fracted stable porous clay gravel for the natural planted. In a pinch use clumping kitty litter (unscented)aquarium.
  - Others say it is OK to use garden sub-soil. Do not add garden compost or fertiliser
• You can use plastic or clay pots filled with rocks for plants that will sit on the floor of your pond or purchase aquatic soil or

Fish

Goldfish: Comets, Shubunkins, ... are an easy way to start.
Koi: Are a little more expensive and complicated.

Recommended Mix
For each square yard of surface area:

• oxygenating grasses (e.g. anachris) - 18" of depth 2 bunches, 24" of depth 4 bunches, 30" of depth 6 bunches)
  See: Aquatic Plant Prices at Hill Haven Greenhouse
• 1 medium to large water lily
• 12 water snails
• 2 fish 4 - 5" (e.g. Golefish: Comets, Shubunkins Sarasas)

Algae

Green water is prevalent during the first 90 days of pond balancing. The length of time depends on many variables such as weather, water chemistry, number of plants and fish, or the richness of your soil.
Your pond may also see a "GREEN" period in early spring, but this should be brief as long as your pond is balanced.
Although plants are a net producer of oxygen, at night they take up oxygen and give off carbon dioxide (CO₂); Levels will usually not change significantly at night, but a severe algae bloom can deplete enough oxygen at night to kill fish. Increased CO₂ can also reduce the pH of your pond.

Natural Control:
Algae needs sunlight, CO₂ and nitrogen.
Add water lilies to reduce the amount of sun reaching the water. Free floating water Hyacinth are inexpensive and will also provide coverage. 50-65% coverage is recommended.
Add oxygenating plants to absorb carbon dioxide. They also produce oxygen during the day to help the fish breath.
Snails and fish eat algae.
Decaying debris on the bottom will produce nitrogen. Remove debris by skimming, siphoning, scooping, vacuuming (use a shop vac or pond vac) or whatever means are available.
A filter will remove most floating algae. Clean your filter every week or so.
However, it's not that simple. See: Green Water: Myths, Facts, Theories

See Artificial Algae Control below.

Problems

Color	Condition	Sympton or Cause
Dark Sparkling green	Good
Dull green to yellow	Not so Good	Disolved Oxygen and pH are dropping. Blue-green algae type becoming predominant.
Gray to black	very bad	Pond is septic. Anaerobic conditions prevail.
Tan to brown	OK if brown algae	However, brown algae can be a symptom of rising levels of Ammonia and Nitrites. Could also be caused by inflow of eroded soil.

Problem	Solution
String algae	S.A.B. and Barley Mats
Green water	Supercharged AquaClearer bacteria & AquaAid Flocculant
Tea colored water	Aquascapes activated carbon

Cloudy Water - Algae and other suspended solids

at Van Ness Water Gardens
Artificial Algae Control:
Ultraviolet Clarifiers kill algae that is suspended in the water by exposing single-cell organisms to intense UV light in a device connected to an external filter pipe. In addition, disease bacteria, fungus, and virus cells are also killed. This doesn't affect algae growing on the sides of your pond.

UV rays strike bacteria, algae and protozoa breaking through the organism's outer membrane. The radiation reaches the DNA of the organisms, causing abrupt modification bringing about their destruction quickly and effectively.

Chemicals
At AquariumPros.com/ they say "Chemicals should never be used to control the growth of true algae in an aquarium, and should only be used in rare circumstances to control cyanobacteria. Correcting a severe algae problem requires time and patience. Natural methods of controlling algae are the best and most effective.

BI-AQUACULTURE is a proprietary blend of all natural biocultures and enzymes which digests/degrades extremely heavy concentrations of organic mass within an aquatic system, reducing nitrogen and phosphorus levels. Info at ThePetStop.com/fish_shop/.
Algicides (Pond Clear) can be used, but they are very rough on plants.

S.A.B. (String Algae Buster) It is fortified with dry bacteria and enzymes; It works by adjusting the micronutrients in the water of the pond resulting in conditions that are unfavorable for string algae. Useful in new ponds until favorable bacteria have time to colonize.

Uberkler, is very effective in eliminating the free-swimming (green water) algae.

Cutrine-Plus is used for filamentous types of algae.

Pond Care® AlgaeFix® [ poly(oxyethylene) (dimethylimino) ethylene (dimethylimino) ethylene dichloride] controls many types of algae including "green water" blooms and filamentous algae that cover the glass, ornaments, plants, and gravel.

Flocculents (clumping agents) (e.g. Aquarem, Crystal Lagoon) are much safer for fish plants and pets.
They are sprayed across the top of the pond, where they form a white cloud-like layer at the surface. This layer slowly sinks, catching suspended material and algae as it drops. (It's best to leave any pumps off during this part of the process.) The resulting layer of sludge can be removed by siphoning or filtering.
Crystal Lagoon is a poly electrolyte that uses a derivative of chitin that is a single chain polymer of immense molecular weight and dense electrical charges. The charges act as hooks, gathering up suspended material in the water to "flocs" or flakes that can be filtered.
Barley Straw - As the straw decomposes in the water, it releases peroxide which inhibits algal growth. See: ianrpubs.unl.edu/wildlife/nf429.htm

See: Water Care Products at WaterTropicals.com/, Van Ness Water Gardens

The average pond should maintain a PH of 7.5 to 9.5 with 9.5 giving the least amount of algae growth.

Pond Chemistry - Disolved chemicals - pH etc.

Nitrification

Ammonia is excreted by the fish gills as well as the normal food excrement. In a mature pond a class of bacteria in the biofilter removes the ammonia almost as soon as it is formed. The ammonia (NH₃) is converted into other nitrogen chemicals called nitrites (NO₂).

Another type of bacteria also present in the biofilter then converts the nitrites into nitrates (NO₃), which is less polluting and toxic than either ammonia or nitrites - both of which are poisonous.

However, nitrates are fertilizer for plants and can lead to more algae.

See: Nitrogen Cycle

Maintenance

Winter Preperation

Other Chemical measurements

GH (General hardness) Rrefers to the dissolved concentration primarily of magnesium and other mineral ions.
A GH between 50-100 ppm is best

KH (Carbonate hardness) KH is basically the buffering capacity of your aquarium, a Kh above 80 ppm helps prevent sudden drops in ph.
Baking Soda (Sodium Bi-Carbonate HCO₃-), is often used for KH.

pH - Alkalinity - Acidity

pH can swing widely during the day, measuring from 6 to 10.
Carbon dioxide (CO₂) dissolves in water to form carbonic acid which has a pH of less than 7 so pH will tend to fall when carbon dioxide is high.
Plants give off carbon dioxide and use oxygen during the night; the reverse is true during the day, as plants consume CO₂ through photosynthesis.
Fish are always using oxygen and giving off CO₂
Waste products decaying at the bottom of the pond give off CO₂.
pH will be lowest in the early morning and highest in the late afternoon.
Large daily changes in pH can cause stress, poor growth and even death of the farmed animals.

Most aquatic organisms can live in a broad range of alkalinity concentrations. The desired total alkalinity level for most aquaculture species lies between 50-150 mg/L CaCO₃

Rocks and cement (which contains limestone) will raise the pH of water. Some people paint rocks with something like Thompson's (r) Water Seal (r) Clear Multi-Surface Waterproofer to avoid

Reducing pH swings:
Aeration - Oxygen levels increase. Carbon dioxide is "blown" out of the water and this tends to push up pH levels.
Add Limestone or crushed oyster shell that they sell for chicken grit. Chemicals to adjust pH:
You should not change the pH one whole unit (e.g. from 8.0 to 7.0) in 24 hrs.
I had a pH test kit which only went to 7.6 and was trying to reduce it with one of the pH decrease solutions from the fish store. It said to put 5 ml for each 10 gallons. I had a 30 gal. tank so started with 15 ml = 1/2 oz. several times and it didn't seem to do anything, so I increased it to 1 oz. then 2 oz with nothing, so put in 4 oz. and it dropped all the way to 6.0. So you need something that will measure higher levels of pH, otherwise you can't tell what is happening.

Test your water hardness before trying to make pH adjustments. If a pH decreaser is added to hard water, it will decrease pH initially, but the pH may swing back dangerously in 24 hours because of the buffering capacity of hard water.
Don't change the pH more than 0.2 per day to avoid shocking the fish.

In addition to chemicals to raise or lower pH there are pH buffers to stabalize the swings.

Acid water (pH < 6.8 can be treated by adding agricultural limestone [CaCO3 and CaMg(CO3)2]. Agricultural limestone will not increase pH beyond a maximum of 8.3. The use of hydrated lime (CaOH2) or quick lime (CaO) is not recommended because either of these compounds can cause the pH to rise very rapidly, to levels that are harmful to aquatic life.

Alkaline water (pH > 8.5) can be treated in several ways:
"pH Down", a liquid sold in pond supply centers for $16/16 oz., claims to neutralize the materian which is causing the pH to rise.
Add White vinegar or muriatic acid.
2 oz of muriatic acid brought my 35 gal tank from 8.2 to 7.2.
Add Alum (Aluminum Sulfate [Al₂(SO₄)₃])
Add Gypsum (calcium sulfate [CaSO₄])
I did some testing:
Alum 4 lbs $8, Gypsum 5 lbs $5
1 1/4 cup of Alum in 2 gal of pond water at pH 9 lowered it to pH 5.
  The Alum added to water from the pond in a bucket remained clear.
  But when I emptied the 2 gal from the bucket into the 400 gal pond,   it caused the water to become very cloudy and lowered the pH to 6.5
1 1/4 cup of Gypsum in 2 gal of pond water at pH 9 lowered it to pH 7.
  The Gypsum left the water very brown.

See: Pond Management-Clearing Muddy Ponds - Adding Gypsum at Texas A & M
Koi Health & pH FAQs

Products:
practical-water-gardens.com/
macarthurwatergardens.com/
www.pondsplantsandmore.com/
pondliner.com/
Algae Control at: Aqua Art, BI-AQUACULTURE
Alkalinity & Hardness In Ponds | UKY.edu