Pond Ecosystem FAQ

Learning about the life in your pond

Your pond is a miniaturized version of what you would find in nature, meaning it has needs and is an ever changing landscape that needs your knowledge and care to thrive.  All the flora and fauna in your pond need a certain balance of elements to insure their safe and productive lives can continue.  This section will give you insight into the inner workings of pond science, it will give you a holistic knowledge that you can use to make sure you are the best caretaker for your pond tenants. Be the best to your pond as you can, so start reading here!

Ecological Questions

Why does foam form around waterfalls? How can it be prevented? Foam indicates a disturbed biological balance with increased pH values. The easiest way to help combat foam is to check the water quality. After assessing the water quality, you can add gravel at the point where the water hits the pond to help decrease the amount of foam.


What causes unusually high water loss? If there is extreme water loss, check the liner for leaks. Make sure to also check all tubing, pumps, and filters to ensure no leaking. Otherwise, it could be a result of water evaporation, which depends on many factors such as sunlight, humidity, wind, and absorption by plants. High winds can lead to water loss from a fountain feature. It’s also possible to lose water from the splash out of a waterfall or fountain. In extreme cases several inches daily could evaporate. There is no fixed calculation formula.


How can pond mussels help clear my water and what must I consider when putting them in my pond? Pond mussels are great because they "filter" the water. Over winter, a minimum pond depth of 6 ft. is required and because pond mussels like to bury themselves, a floor of silica sand or gravel is also recommended. We suggest you don’t have koi or large goldfish while you have pond mussels.


What should I consider to establish a functioning ecosystem for my pond? The following values are used to assess the water quality:

  • pH value

  • Carbonate hardness

  • Total hardness

  • Nitrate/Nitrite content

  • Phosphate content

  • Dissolved Oxygen

Use a water tests to make sure your water quality is where it should be. Ideally, you should test your pond’s water every 2 weeks, increasing the tests if you have an issue. 

TIP! Every time you use a new treatment or maintenance method, observe how your ecosystem changes (your fish die, plants grow faster, etc.) and tailor your routine to those results. 


What can be done to either protect against or fight increased algae infestation? There are many causes for algae growth, including excessive nitrate and phosphate concentrations caused by overfeeding or decaying organic debris. Additional causes include, an excess of uneaten food, fish waste, too much direct sunlight, warmer temperatures, excess rain or overcrowding of fish.


What "natural methods" are available to guard against increased algae infestation? Adequate number of pond plants (at least 1/3 of the pond surface) and added pond bacteria help to regulate excessive nutrients.


What is the easiest way to lower or regulate the pH value of a pond? One reason for excessive pH value can be the expelling of carbon dioxide through intensive aeration and waterfalls. Minimizing the water flow through the waterfall, and rearranging the pumps could help. Likewise all types of concrete blocks and sand-lime brick have an effect that increases pH value. A change could contribute to regulating. Another tip: Garden pond peat helps reduce excessive pH values.


Is there a remedy for string algae? It is your best bet to simply fish the algae out, or using grass carp to graze on it. By the way: As opposed to suspended algae, string algae is an indicator of "healthy water".


Do UV bulbs really help against algae infestation; what if the pond gets a lot of sunlight? Yes, however only against suspended algae that makes the water murky; they do not help against string algae. UV denatures the proteins in algae, causing them to stick together (flocculate) and then can be picked up by a filter or skimmer. A UV bulb by itself is only of little help as it only flocculates the algae. There must be a filter downstream from the UV bulb that filters out these clumps of algae. You will find the suitable filter in the OASE product offerings.


How many fish can be in a garden pond? A good rule of thumb is approximately 1 inch of fish per 10 gallons. However then you must include future growth in the calculation. The fish stock should be checked annually and corrected as needed. Excessive fish stock can cause murky water, algae growth, plant damage, and fish disease.

Do fish need to be fed the entire year? Fish are cold-blooded animals, e.g. when the water temperature decreases their metabolism slows and the need for food decreases. Koi can’t metabolize food under 50 degrees Fahrenheit. You should start decrease feeding once it gets below 60 degrees Fahrenheit.

How can I determine the sex of koi? Male koi are mostly thinner and usually have larger and more pointed pectoral fin and the vent opening is a slit form. In our climate sexual maturity is reached after 3 – 4 years. Female koi are rounder, have smaller pectoral fins and a round vent opening. Sexual maturity is reached in approx. 4 – 5 years. At sexual maturity, females are larger than males. Precise identification is not possible for young fish.


How long does it take for a koi to get used to the new pond? Habituation times of up to 14 days are normal. It is important to leave the koi alone. Stress and hectic net movements are better avoided at this time. 


What are the general conditions for pond plants? The best planting period is in spring (starting in March). For near natural planting we recommend making different-depth plant zones. The following guidelines apply: 

  • Marsh zone (damp zone): 0 to 10 cm

  • Flat-water zone: 20 to 50 cm

  • Deep water zone (water zone): deeper than 50 cm

The rule of thumb for plant quantity: approx. 1/3 of the total pond surface should be planted to prevent an overabundance of nutrients. Plant baskets or plant mats are recommended as planting aids.


What makes an optimal pond floor, or what is suitable as a plant substrate? Gravel as well as sand is suitable for the pond floor or plant substrate. When deciding be aware that sand silts up sooner than gravel. On the other hand with fine gravel, any decaying organic matter settles in the cavities, which makes cleaning more difficult (a sludge vacuum is useful in this situation).


Which gravel types are recommended? Sandstone gravel or other similar silica stone is recommended. We do not recommend limestone gravel like marble gravel. They shrink in size overall and can raise pH levels. By the way: The pond floor does not have to be totally covered with gravel; in time a layer of pond sediment will form on its own.


Can the individual stones give off substances that are harmful to the water? A general tip: There are no problems with anything in the direction of sandstone, because the stone (of silica and quartz) cannot give off substances that affect the water. 

Is the brief "blossoming time" of my water lily normal or is the plant sick? Water lilies bloom for only a few days like many other plants – this is normal for a healthy plant.


Which underwater plants are particularly recommended for koi? We recommend not having any underwater plants if koi will be in the pond (they will be quickly torn up or eaten).


What do I need to be aware of when planting water lilies? When planting, the water depth specified on the plant label must be maintained. A little special fertilizer (adhere to dosage directions as an overdose can be harmful to fish) promotes healthy growth.
In addition the planting location should permit sunlight and you should check the oxygen content of the pond water.


Can normal land plant potting soil be used in the plant baskets for water plants? Preferably not! Normal potting soil contains too much fertilizer (can also be the case with pond soil). To completely avoid the risk of fertilizer stress it is best to use normal gravel as planting substance. Another low-nutrient alternative is pure clay.


Do plant baskets help or hinder plant growth? Generally plant baskets are helpful because they prevent the roots from extending freely and damaging the pond foil. Please note that the soil should be filled up from time to time and covered with gravel (this prevents churning up).


Can water lilies and other floating leaf plants survive with decorative water effects? Water lilies and other floating leaf plants cannot survive with excessive splashing water – water effects like fountains should accordingly be placed far away from these types of plants.