A) Depth of pond: A deeper pond (>1m) prevents koi from being affected by fluctuations in temperature due to weather. (Shallow pond water with big surface area will be heated up much easily than a deeper pond with smaller surface area)
B) Filter System: A proper filter system setup is one that allows waste to be effectively discharged with ease. It is also one that contains replaceable filter media (as filter media needs to be replaced every few years due to wear and tear) that both take care of mechanical & biological filtering needs.
C) Number of Koi: No over-crowding of fishes.
D) Shade: Providing a shade if possible either using landscaping or shades with <40% sunlight shining into pond.
E) Choosing a reliable contractor with genuine testimonials & good track record: A proper pond construction company should be able to answer all your queries with regards to construction & maintenance. The company should also be able to provide you with koi keeping advice and maintenance services.
Koi ponds with big water volumes are usually more stable as a hot sunny day and cold night will not affect the temperature of the pond water too much. In a shallow pond (especially one with a big surface area) with full sunlight, temperature changes can be quite drastic between the day and night. Kois always tune themselves to the temperature of the water they live in and sudden changes may lead to stress (and low immunity) which in turn provide an opportunity for bacterial infections to set in. Kois are also able to exercise in a deeper pond propelling up and down whereas in a shallow pond, you would usually see their bodies being more irregular or obese in shape.
Photosynthesis is a process whereby plants (including algae) harness the energy of light combined with Carbon Dioxide to produce food. During the night, the process will reverse and plants (including algae) will then be responsible for taking in Oxygen and releasing Carbon Dioxide. Through air exchanges between pond surfaces (so be careful if you have a wide surface and shallow pond) and the atmospheric air, oxygen will be stripped to the atmosphere. To make things worse, if one were to overcrowd kois in a small pond, both kois and beneficial bacteria living in the bio-filter will be struggling for oxygen in the pond.
It has come to our attention that there are companies constructing under-gravel filter system (ponds with little stone gravel/pebbles on the pond bed) for fish ponds and claiming that ponds only require maintenance once a year. This is not a suitable or sustainable setup for outdoor fish ponds. A simple reason on its unsuitability is due to the fact that the system pulls fish waste & dirt towards the pond bottom and there is no effective way to discharge them. Instead of being a biological filter for the pond, the gravel then becomes a toxic bed for the fish. There are many articles on internet describing its cons in detail which you can research before making your decision.
The water in Singapore contains Chloride and residual Chlorine in the form of Chloramine. Although Chlorine (which is a volatile gas) will dissipate when exposed to air, Chloramine takes a much longer time to break down. Chloramine will kill the nitrifying beneficial bacteria within your filter chambers and can also wipe out fish in large amounts. Thus, it is very important to keep a bottle of good anti-Chlorine and anti-Chloramine concentrate handy whenever you perform filter maintenance or water change.
There is no hard and fast rules on the frequency of water change and filter maintenance. It depends on factors like the number of koi you have, size of your koi, frequency and amount of feeding, type of food etc. It is recommended to clean your filter once a month and some hobbyists even do 10% water change on a weekly basis. This is the only way to reduce the nutrients in the water in a closed loop pond system.
Algae contain chlorophyll and can photosynthesise given the right conditions (water, Carbon Dioxide & sunlight); all of which are abundant in an outdoor koi pond. In an outdoor pond, the water is nutrient-rich due to the waste from the koi, which makes the environment even more favourable for algae to bloom. There is no way to completely remove these nutrients, thus, providing a shade or frequent water change/filter maintenance helps.
We do not recommend the use of chemicals to remove algae in the water as it is a temporary measure and not beneficial for the koi.
pH (Potential of Hydrogen) is a measure of how acidic or alkaline a solution is. Although koi can tolerate pH of 7.0 – 9.0, hobbyists will avoid acidic (acidosis) and extreme alkaline (alkalosis) conditions. In case of acidosis condition, fishes tend to be agitated and frequently jump. When pond water is under alkalosis condition, it will usually hurt the gill and fin.
There is a misconception that mosquitoes will not breed in a water feature as the water is constantly moving. However, there are dead spots in a water feature (eg. Corners of the pond, behind the water spout etc) where mosquito breeding is definitely possible.
Use a good quality chemical compound weekly for water feature to prevent mosquito breeding and growth of algae. It is also recommended to drain and refill non-fishkeeping water feature once every 3 months according to HSA standards.