Spring is arguably one of the trickiest times of year for garden pond owners. The season brings the welcome return of warmer days and longer hours of sunlight, encouraging home gardeners to get out there and enjoy the outdoors. However, temperatures still fluctuate and can be rather unpredictable – blurring the clear distinction between “winter” and “spring.” Straying from best pond practices can allow Mother Nature’s erratic behavior to cause a range of problems on fish health.

Pond with healthy fish

Spring is a critical time of year for pond fish. Help them come out of dormancy by feeding them the proper diet and keeping the water garden clean.

Photo Credit: Courtesy of TetraPond

Koi mix in clear water

Keeping water quality high will help keep your fish in good health.

Photo Credit: Courtesy of TetraPond

Large pond fish

Take the time to help your garden fish properly come out of hibernation – you’ll be rewarded with a thriving water garden filled with life, movement and color.

Photo Credit: Courtesy of TetraPond

Koi in pond

Because pond fish are cold-blooded, the water temperature controls their metabolism and activity level.

Photo Credit: Courtesy of TetraPond

Because pond fish are cold-blooded, the water temperature basically controls their metabolism and activity level. This is precisely why feeding fish according to the water temperature is so critical. Following a seasonal feeding cycle will eliminate any guesswork and keep fish in good health and condition.

To transition your pond fish from winter dormancy, feed them a wheat germ diet once or twice a day, when water temperatures are at 39-50 degrees F. Wheat germ is highly digestible (resulting in little waste). This is especially important because in the colder months, fishes’ metabolism and the pond’s ammonia-reducing biological activity are greatly diminished. Once the water is above 50 degrees F, you can feed your fish a higher protein staple diet.

Despite your best efforts to help your fish transition into the seasonal change, remember that “sick happens.” In the spring, fish immune systems are delicate and pathogens are ramped, leaving your pond pets more vulnerable to disease. Pond fish flourish in warm water, and their immune systems tend to work best at higher temperatures. Because their immune systems aren’t up to full speed once spring hits, fish in cold water temperatures are physically stressed and vulnerable to common pathogens (disease-causing microorganisms).

Additionally, water quality is typically less stable, especially if temperatures fluctuate dramatically, because the activity of filter bacteria is also governed by temperature. A sudden increase in temps will increase fish feeding levels, which will in turn increase ammonia production. (If the filter bacteria cannot adapt quickly, ammonia will accumulate. This is most likely to occur when filters are too small, not maintained properly or if they’ve been turned off for part of the winter.) Preventing the deterioration of water quality will help you keep your fish in good health.

Follow these measures to keep your fish healthy from the start of spring:

  1. Feed your fish a premium quality food that helps to maintain their energy levels. Feed according to a seasonal feeding cycle, with as much as fish can eat in a few minutes. If ammonia and nitrite levels in the water are high (greater than 0.25 mg/liter and 3.0 mg/liter respectively), reduce feeding and conduct partial water changes until the levels are normal again.
  2. Get your filter up and running, if it isn’t already. Make sure it’s free from debris so the filter bacteria recover and work more effectively. Biological filtration, for example, colonizes beneficial bacteria, which converts harmful ammonia into nitrates that fertilize plants and are relatively harmless to fish. Comparatively, mechanical filtration uses foam, screens and/or matting to physically trap dirt and debris and prevent buildup. To further ensure clear water, you can install a UV clarifier to eliminate suspended single-cell algae that cause “green water” and destroy its reproductive ability.
  3. Test the pond water (mainly for ammonia, nitrite and pH) and observe your fish more often so you can identify any symptoms of water quality or health problems – and respond quickly if you notice anything. Excessive ammonia greater than 0.25 mg/liter can cause severe signs of irritation and occasionally reddening of the skin and fins. Likewise, nitrite levels greater than 3.0 mg/liter can cause irritation of the gill and skin membranes, as well as a reduced ability of blood to transport oxygen. Nitrates, though unlikely to be directly toxic to pond fish unless the concentration is greater than 50 mg/liter, can also make fish prone to disease, poor coloration and poor growth.
  4. If a severe water quality problem is detected, it’s time to administer a water change that’s 50 percent of the pond’s water volume. For less severe water problems, changes of 15-25 percent should suffice.
  5. Seemingly harmless tap water also poses a threat to fish, as it contains chemicals and heavy metals that are dangerous for pond fish. When changing the water in your garden pond, use a water conditioner that neutralizes harmful chlorine and chloramines, as well as binds and detoxifies the heavy metals commonly found in tap water. (Some tap water treatments also provide a colloid coating for fish, protecting their sensitive gills and membranes and helping wounds heal quickly.)
  6. Keep a good quality general pond fish treatment on hand so you can treat any emerging problems. (The most common diseases at this time of year should respond well to treatment.)

There are many reasons to celebrate the coming of spring – the start of a new gardening season being one of them. We may be ready to get out there and enjoy outdoor living to its fullest, but for pond fish, this change in season is a delicate transition. Take the time to help your underwater friends properly come out of hibernation. Your fish – and water garden – will thank you for it.