5 Reasons for Fish Dying in Your Pond (and How to Solve it)

5 Reasons for Fish Dying in Your Pond (and How to Solve it)

It is natural to find dead fish in your pond occasionally, as they might pass away due to old age, a minor disease, spawning stress, or handling. However, if many fish are dying in the pond, you may need to get to a root cause to protect any remaining or new fish.

If you’re unsure about the potential problems, here are five possible reasons fish are dying in your pond, as well as advice on how to solve it.

Reason #1: Oxygen Issues

Reviewing a pond’s oxygen level is the first step you must take. Check if the pump or filter is still running and if the waterfall or fountainhead has affected the water. If you’ve experienced warm nights or added plants around the pond, it may have depleted its oxygen levels and killed the largest fish.

Bear in mind some fish are more affected by depleted oxygen levels than others, such as golden orfe. As a result, they might be the first fish species to pass away. Buy an oxygen test kit to review the levels at night. If the oxygen levels are too low, you may need to change pumps to protect your remaining fish. Visit water-garden.co.uk to find the best quality pond equipment.

Reason #2: Water Quality

If a pond’s oxygen level is fine, the water quality might be to blame for fish dying. Ammonia, nitrate, and nitrite are toxic for many fish, which is why you must use a water testing kit to review the water quality.

The pH should be between seven and eight, and nine or higher will prove the water is contaminated. If this happens, change at least 30% of the pond water to improve its pH levels and care for your remaining fish.

Reason #3: Water Temperature Fluctuations

If you’ve crossed off the above reasons, you might be scratching your head about the pond’s problem. Water temperature fluctuations might be the cause, as sudden or severe heat or cold can cause much stress to fish, which may increase their susceptibility to disease, higher ammonia, or low oxygen levels.

Keep your fish safe and healthy during severe weather conditions by:

  • Providing shade over the pond
  • Monitoring the water levels
  • Keeping the water well oxygenated
  • Ensuring the pond is at least two feet deep
  • Placing a hole in any ice
  • Using a pond de-icer during cold temperatures
  • Adding a pond cover during winter

5 Reasons for Fish Dying in Your Pond (and How to Solve it)

Reason #4: Overcrowding

Overcrowding is a common cause of fish death in a pond. Adding too many fish will reduce the oxygen available, and increased waste production will boost the ammonia and nitrate levels. Monitor the nitrite and ammonia levels to identify overcrowding. If it rises above zero, it’s a warning sign your pond is overcrowded.

Reason #5: Overfeeding

If you have ruled out all the above possible reasons, overfeeding might be the culprit. It might surprise you that fish are more likely to die from overfeeding than from missing food. The fish may not consume all the food in a pond, and the leftovers may rot at the bottom.

Avoid overfeeding by removing any leftover food within five minutes of adding it into the pond. If you have a busy pond, add small pinches of feed a couple of times per day instead of one large amount, ensuring the food doesn’t go to waste.