Summer is a wonderful time of year to enjoy your pond. The fish are active, the weather is warm and there are more daylight hours for you to enjoy. Like every season, summer brings unique requirements for maintaining your pond and caring for the koi that call it home. These are some tips for getting the most out of your summer experience, and keeping your koi healthy and happy during this sunny season.

DON’T Overstock

The summer months can really showcase your pond’s beauty, which can make it tempting to add a few more residents to your pond. However, overstocking your pond can lead to water quality issues and stress and illness for your pond population, so it’s important to make sure your pond is large enough to accommodate new additions. A koi pond should contain at least 1,000 gallons of water with 200 gallons of water per additional fish. The pond also should be at least three feet deep, as depth helps prevent freezing and drastic fluctuations in temperature (if you live in a climate that gets cold in the winter you may need a pond up to six feet deep).

DON’T Overfeed

Koi are more active during the summer and will eat more food, but be careful not to overfeed. This can be particularly tempting when you are around them more, especially if you often entertain guests who will want to feed them. Excess food accumulates in the pond and can cause significant water quality problems. Your summer temperatures will dictate the number of times you feed per day, which typically should be one to three depending on where you live. Feed only as much as your fish will eat in three to five minutes.

DO Provide Plenty of Shade

Koi can survive in water temperatures up to 90 degrees, but that doesn’t mean such an environment is comfortable or healthy. Pond plants are an important part of the summer pond setup, as they provide shade, cool the water, and contribute to biological filtration. Plants like water lily, lotus, and water hyacinth are great options for shade-providing plants that help keep water temperatures down. They also hide your fish from predators that are more abundant in the summer.

However, overgrowth is common in the summer, and too much of a good thing can have the opposite effect. Aim to cover between one-third and one-half of your pond’s surface with aquatic plants, but no more. If plants proliferate beyond 50 percent you will need to remove some of them or nitrate levels may rise too high.

DO Test Water Regularly

Maintaining a healthy pond requires routine water quality checks. You should test water for pH levels, ammonia, nitrites, and nitrates, all of which can harm fish when out of balance. This can be especially important in the summer months when the pond experiences elevated waste and plant growth, as well as warmer temperatures. It is still important to keep pH levels between roughly 7.4 and 8.4, ammonia at 0, nitrates at 20 to 60 ppm, and nitrites at close to 0.

How often you need to test will vary depending on your pond size, the number of fish, and the filtration systems you have in place. Some ponds will require weekly testing, while others can easily go for two weeks or maybe even a month between tests. However, you should test immediately any time you notice fish exhibiting concerning behavior, changes to the plant covering, or any unusual smell coming from the pond.

DO Replace Evaporated Water

During the hotter months, your pond water will evaporate at a much higher rate. Therefore, it is important to maintain the water levels in your pond by supplementing it with clean, dechlorinated water. Adding cooler water during changes can help with temperature — just be mindful that large temperature fluctuations can harm your koi. Also remember that a water top-off does not factor into the percentage of water you change each week, which should range from 10 percent to 20 percent depending on your water parameters.

DO Keep Oxygen Up

Oxygen levels should be at a minimum of 5.0 mg/L for koi, with 18 mg/L being the physical maximum that water can hold. A pond with a 90-degree water temperature holds only about 7ppm (parts per million) of dissolved oxygen in the water. Levels that drop to 4ppm will stress the fish, and at 3ppm they can be fatal.

Warmer water holds less oxygen than cooler water. Simultaneously, your fish are more active and consume more oxygen when temperatures rise. This combination can cause fish to have difficulty breathing. Test your water temperature regularly, and add oxygen to the pond if it approaches 80 degrees. Behaviors like gasping at the surface of the water and congregating near waterfalls or fountains are signs that your koi are struggling to breathe.

Several options exist for increasing oxygen levels. An aeration pump can greatly improve the amount of oxygen in your pond and will help beneficial ammonia- and nitrite-fighting bacteria that an effective nitrogen cycle needs. A bottom drain also is useful in tandem, because it pulls the water with the lowest oxygen content to the surface where it can be replenished. Air pumps and air stones are additional options for increasing aeration in the summer months. Fluid bed filtration technology is another way to aerate a koi pond. This involves sending air into a basin filled with bio media, providing an oxygen-rich environment.

DO Clear Out Debris

Water is a magnet for wind-blown debris. If you live in a region with high humidity, you are more likely to experience summer thunderstorms that will wash in leaves, branches, grass, and more. Debris will eventually become waterlogged if left in the pond too long and will sink to the bottom, raising ammonia levels. Clean out your pond periodically, but especially after a heavy rain or storm.

Skimmers are a helpful tool for quickly removing foreign objects from the surface of your pond. The primary job of a pond skimmer is to remove floating debris from the surface of a pond before it has a chance to sink. Skimmers act much like the nets used for swimming pools but do the work for you.

DO Control Algae

During the summer, your pond will experience more algae blooms than in other seasons. Algae thrive off the nitrates in koi waste, so they are an essential component of your pond’s ecosystem. However, the increased waste, water temperatures, and sunlight in the summer can cause algae overpopulation. With all the benefits of algae comes the downside of its oxygen consumption that can compete with the koi if it gets out of hand.

You might need to clean your filters and water valves along with your weekly water changes. If algae growth still is a problem, you can add netting or introduce a pond dye to the water. Additionally, you can reduce the protein in your koi’s diet. This will encourage the koi to eat the algae. A skimmer also will help control pond algae.

Is your pond ready for a few new additions? Shop our full selection of koi and pond goldfish today.

4 responses

  1. charlesgodfrey :

    my koi pond is 8’wide,11’long,4’deep,filted,aerated,4’waterfall, how many koi will it hold, answer question

  2. doug leblanc :

    i bought 7 koi from you and received them around feb. 26. I quarantined for about 10 days, put into my pond and things were great until 2 days ago. two of the koi were floating near the top of the pond, I took them out and quarantine them . One is doing great and the other died today, :(. sad day. could he have had bad genes or something, compromised immune system maybe?

    1. Hi Doug,

      We are very sorry to hear of the issues you have described with the fish from your recent shipment. We will reach out to you via email shortly.

      Thank you.

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