10 Most Frequently Asked Questions About Ponds
by a Petstore Staff Member

1. How deep should my pond be?

As a general rule 24” to 30” is usually adequate to support a healthy collection of pond plants and fish. Koi ponds should ideally be five feet or deeper to promote proper muscular development, and should be constructed a minimum of three feet deep. Deeper ponds also help maintain a consistent water temperature throughout the year and will help provide protection against predators such as raccoons and herons.

2. What’s the difference between a water garden and a Koi pond?

This is an important question that all hobbyists should know the answer to before even starting construction. A water garden is typically built with emphasis on plants, a few fish and mainly the overall aesthetics that the water feature will bring to the existing landscape. Container gardening, reflection ponds, and combination ponds fall into this category. A Koi ponds main focus and purpose is the construction of a feature that will maximize the overall health and prosperity of Koi. Major emphasis is put on the equipment used in these types of ponds because they are the “backbone” of this type of system. Products such as bottom drains, bio filters, aeration devices etc, need to be carefully researched and matched correctly with each individual system for long term success.

3. Do I need a filter?

Proper filtration is essential to the maintenance and overall success of a pond. Many different types of filters exist on the market today but the type of pond you build will determine the type of filter that should be purchased. A good pond filter will contain both mechanical and biological properties. Mechanical filtration is used for the removal of solids. Biological filtration is used for the removal of dissolved waste in the form of ammonia and nitrite and conversion to nitrate, a less toxic form. In addition to filtration, plants and/or water changes are necessary to remove nitrates, the end product of biological filtration.

4. Should I put rock or gravel in the bottom of my pond?

Probably the most frequently asked question in the beginning construction phase and one that always starts a heated debate. Most Koi driven hobbyists will tell you absolutely not. Gravel can impede the flow of water into bottom drains and maintenance of gravel can be difficult and if not systematically cleaned can lead to organic buildup in the pond. If you do decide to use gravel, keep the gravel layer thin(less than one inch thick) to avoid anaerobic conditions.

5. How often should I change the water in my pond?

Small gradual water changes are always preferred over large quick water changes. In a properly filtered system, a water change of 10% to 15% every 2 weeks is normally sufficient. In ponds where larger amounts of fish are being stocked or in under filtered situations more water changes may be required. Always remember to use some type of dechlorinator after every water change and never perform a full water change on any system as undoubtedly you will do more damage than good.

6. How often should I feed my fish?

Overfeeding is one of the most common mistakes hobbyists make. Uneaten food can lead to toxic ammonia levels and can quickly diminish overall water quality. Proper feeding techniques are especially important when dealing with Koi and goldfish due to their lack of a refined stomach and the fact that their metabolism is governed by the water temperatures they reside in. As a rule of thumb feed fish only what they will eat within 5 minutes and remove that which is not eaten. Feed your fish more during the summer and less during the winter and do not feed when water temperatures are below 50º F. For a more in depth explanation of what and how often to feed your fish, please refer to our Feeding Your Koi article in this section.

7. Can Koi and goldfish live together?

All Koi and goldfish are peaceful schooling fish and as such readily accept new members to their “family”. Koi can outcompete varieties of “fancy” goldfish for food sources which can lead to starvation, but careful observation of whether these types of goldfish are getting enough food will quickly remedy this issue. When mixing fancy goldfish and Koi keep in mind that most Koi ponds are built quite deep and while suitable to the Koi they were built for; varieties of fancy goldfish can experience swim bladders issues associated with these deeper pond depths.

8. What should I do if my pond water is green?

Green water is caused by a single celled floating algae that gives the appearance of what some call “pea green soup”. This type of algae is quite common when ponds are first built before natural sources of bacteria have had a chance to develop. The use of commercially available bacterial products can help aid in the growth of natural bacteria, reducing “cycling” time and can be quite helpful in this situation. Overstocked ponds, under filtered ponds and ponds in full sun can also exhibit this characteristic. Usually by increasing filtration or adding a UV light will quickly remedy this situation. As a general rule ponds that are built in full sun always have some type of algae issues and should be avoided at all costs.

9. How do I get rid of string algae?

Keep in mind that a natural growth of a structured green algae is a necessary and beneficial occurrence in ponds. This algae provides a natural food source to all pond fauna and is a sign that the natural process of the pond are functioning correctly. However string algae can be considered a problem if it grows to lengths of several inches, when it can choke out plants, plug filters and generally create an eyesore. Chemicals can be used for temporary removal of string algae but long term results can only be achieved through proper husbandry techniques. Removing dead or dying material either through mechanical filtration or manual removal on a consistent basis is a must. Aquatic plants can help provide shade which can reduce excessive light. Aquatic plants also use the end by- product of biological filtration; nitrates, as a food source and by use of the correct amount of these plants will use up this available nutrient before forms of noxious algae can utilize it.

10. How long do Koi live and how big do they get?

There are accounts of Koi being passed down from generation to generation, literally living hundreds of years. In perfect conditions a more practical life span is more like fifty to seventy years. Koi are considered mature once they reach about 36” in length. Of course they have been known to achieve much greater sizes and Japanese Koi that have had the luxury of being brought up in mud ponds and fed an optimum diet their whole lives frequently reach 48” in length. Obviously factors such as type of diet, water quality and size of the pond have direct and permanent affects on the size a Koi can ultimately reach.