Fish Kill

How to Avoid Fish Kill

Aug 9, 2013 – Pond owners stock their ponds with fish for a number of reasons;

  • To raise and eat them as a source of food
  • To raise and fish for them as a form of recreation
  • So that the fish will control the amount of algae in the pond by eating it
  • So that the fish will eat the mosquito larvae that is floating on surface of the pond
  • To act as a food source for surrounding wildlife
  • For the shear beauty of nurturing wildlife in their ponds

A simple measurement to go by in order to determine the appropriate number of fish to stock in your pond is to add one fish for every square foot of surface area in your pond.

Now that you have your pond stocked with fish the next challenge is to ensure that they stay healthy and alive. Fish kill can be caused by a number of factors and the presence of dead fish in your pond should be taken seriously. A pond owner should act quickly to determine the cause.

Potential Causes of Fish Kill

  • Is there any other water entering your pond and is there runoff coming into your pond? If so perhaps a toxic substance has entered into your pond water.
  • How many fish are in your pond? Could it be overcrowded and if, so perhaps a lack of food exists to feed all the fish.
  • Has there been a heavy rain storm in the middle of an extremely hot weather stretch? If so perhaps your water has turned over and depleted all of its oxygen. If this has happened you would see a mass fish kill, not just a few being affected.
  • Have you had extremely high temperatures making your water very hot and reducing the water’s oxygen levels.
  • Does your pond have high amounts of algae? If so this can also deplete the level of oxygen in your pond, causing stress on your fish.
  • Does your pond have high levels of nutrients and organic matter such as phosphorous? If so this can take up a lot of oxygen in your pond not leaving enough for all your fish to survive.
  • During spawning season you may also have some fish die due to the stress it has on the fish.

Many regional governments track the number of reported fish kills in their regions and its been found that the majority of them could have been avoided by simply providing additional levels of oxygen in the ponds. Pond aeration is a critical component to maintaining a clean, healthy pond which in turn will keep your fish alive. Having said that if your pond is extremely shallow like 2-3 feet you should consider digging out an area that is 8-12 feet deep – this will give your fish an area of the pond to go to that is cooler so they do not bake in the heat. By aerating this area of the pond with a bottom up pond aeration system you will provide oxygen to your fish and also circulate the cooler water around the pond which will help bring down the pond temperature. There are both windmill aeration and electrical aeration systems that can help you with this.

The second highest cause for fish kill is pollution. Pollution from industrial waste, pool overflow, sewage inflow, runoff are some of the key contributors to pond pollution. Again, depending on the severity of the pollution in flow, pond aeration can help minimize the damage it causes on fish by ensuring the pollution is burned out of the water source before it kills all the fish.