In a healthy pond, with a properly functioning nitrogen cycle, water changes can be minimal. I still recommend a water change of 10-20% per month on a healthy, fully functional pond. In a newer pond larger and more frequent changes may be necessary.
If your pond has a KH below 80 ppm and a pH below 7.0, I would first look to possible causes. One common one is the buildup of organic mulm on the bottom of the pond. The decomposition of this will produce nitric acids which will affect the pH and KH. Since most pond keeper have koi or goldfish, this is important to note, as both these fish do much better at a pH above 7.2 and need the calcium provided by the KH for proper osmotic function. See “Proper Calcium, Magnesium and KH in Aquariums” for more information about Calcium KH, and GH.
If a lot of leaves fall to the bottom of the pond vacuuming them or raking them out is important to prevent organic buildup.
Water changes also will help with pH and KH if your tap or well water is slightly alkaline and has a KH above 80 ppm.
Feeding a quality diet can be beneficial for growth, breeding, color, and eve the environment as there is less nitrogenous waste to add to the water column.
You want a food high in aquatic based proteins (although not too high in protein as most koi and goldfish are more “grazers”). Whole fish meal or white fish meal is a good source. An amino acid that is important to koi and goldfish is DL-methionine and is found in Whole fish meal as well as peas.
Cereal is not a good source of energy for fish as it is in humans, fish utilize fats more for energy. Cereal is mostly used as roughage and to move other nutrients thru the digestive tract.
In summer months I usually feed twice per day, as temperatures fall below 70 F in the pond I feed once per day. When temperatures fall below 60 F in the pond I feed every other day or less, depending on fish feeding habits. Below 50 F, I do not generally feed.
For adult Koi there are several quality foods available: Hai Feng, Sanyu, A-Zoo, Hikari, and Nursery-Pro just to name a few. For goldfish or shubunkins I recommend Spirulina 20 Flake, Hikari, or Sanyu. For fry (in addition to natural foods that will be available around the plant roots and other calm areas of the pond), I powder Spirulina Flakes and stir it into a cup of water, then pour this solution into the area the fish fry are at.
*Winter Pond Care
It is important in winter to keep at least a small section of your pond open for proper exchange of gasses (O2, CO2), if water can still flow into the pond through a water or aeration device, that will work. However if you live in an area of hard freezes, you may need a pond de-icer
Generally most Pond Fish such as Koi and Goldfish like a higher ph of about 7.8 (although a pH in the range of 6.8 to 8.0 is often acceptable). A well planted stable pond usually does not have problems with too high or too low a pH.
If your pH is too low, Sea Chem Marine Buffer can help (Wonder shells somewhat too). For large volumes of water, aragonite may be more cost effective.
For too high a pH, these are cost effective ways in a pond:
-Barley Straw (great for algae control too, although so-so for ph)
-Almond shells (this is really good for lowering ph, more effective than peat and with the side effect of being antibacterial)
-A veggie filter (this helps with a stable pH and produces nitric acid)
Construction and make up of your pond can be done in three different ways (and there is no one best way; the best way fits your pond size needs, climate and budget).
A preformed pond is probably the most simple. With this method you basically dig a hole to the shape of the pond, remove sharp rocks, add sand for a cushion maybe cut a few holes on the size for bulk heads to add filtration and you’re ready to add rocks, filtration and décor. This style is good for small applications (usually under 250 gallons) and where roots or gophers may be a problem.
A pond liner made of PVC material or EPDM. I prefer the EPDM in a 45 mil. thickness.
With liners you can generally go up to a 1000 gallon pond. Preparation is similar to a preformed pond, however more care needs to taken with sharp rocks and a pre liner or sand should be used. Also in areas of high tree roots or gopher activity these can be compromised.
The other method is a concrete pond using rebar for support as well. This is probably the most expensive method however this is the method I recommend over 1000 gallons. I have subcontracted (installing the filtration) for many concrete ponds and it is important to use a good contractor or prepare and build this properly yourself as even a concrete pond that is poorly built can have problems. Make sure to not build a concrete pond on “fill” as the pond will often settle and *****. Also proper use of rebar is a must especially in ponds over 3000 gallons.
I personally usually do not had a substrate per say, rather I allow the roots of potted plants (that will grow out of there pots) to collect there own debris. I do often add some zeolite or laterite both for absorption of some nutrients but also as an inexpensive plant root material.
*Spring Fed Pond
If you live in an area of natural springs or have creek flowing nearby, this can make for a very healthy, clear and natural pond. If it is possible to divert water into your pond (or just fill from below with a spring), this is always an excellent idea! This way you will likely maintain lower nitrates and phosphates, less algae, better Redox, and better electrolyte levels resulting in a more clear pond and healthier fish. Make sure to have an overflow or skimmer to remove excess water. If you have a well you can achieve similar results (or even use your well during the dry season when the spring or creek diversion dries up).
I also have achieved a similar effect with just plain tap water used in a very slow flow (a 10% water exchange per day or less will not show any ill effects from chlorine). Make sure this is not a problem with local water companies first, although the ponds I used tap water overflow on used less than 200 gallons per day (for a 2000 gallon pond) which is less than watering one’s lawn for an hour.
If with this method, filtration and circulation are still needed in my experience, although this often allows for a more simple filter (such a the Hydro-Pond Sponge Filter). A Veggie Filter is very usefull in this set-up too!
Herons have been the most common predator to my customer’s ponds that I have had to deal with. I do not like to add anything that detracts from the beauty of the ponds I maintained, so decoys were my first choice. I found Heron decoys worked well at not only scaring away Herons, but other predatory birds as well such as Cormorants. I also occasionally employed motion sensor scarecrows that connected to a water supply and then ******** ANYTHING that moved, this device also worked for dogs that would “play” in the pond (often destroying it and scaring fish), but was not as effective for raccoons.