When your fish start dying in your outside pond, you might start freaking out. In order to fix the problem and keep your pond fish healthy, it is important to find out what is causing them to die. Read below to find the most common reasons fish die in outside ponds. 

Why are my fish dying in my outside pond

The main reasons that fish are dying in an outside pond is because of water quality, too many fish, overfeeding, and fertilizer pollution.

Poor water quality

Having poor quality is one of the main reasons your fish are dying in your outside pond. There is a good chance your pond has low levels of oxygen. There might also be the presence of harmful chemicals, such as nitrate or ammonia. We recommend testing your pond pH if you suspect your fish are dying from poor water quality. A good pH level for an outside pond is 8, but 7 and 9 are also acceptable. Another sign of poor water quality is your fish staying at the top of the pond. If your pond is low in oxygen, you should invest in a water pump which will increase oxygen levels. 

Too many fish

Another common reason fish die in outdoor ponds is because there are too many fish living in too small of a pond. They begin to compete for food as well as other resources in the pond, which causes the losers to usually get sick and die. The general rule is to have 20 gallons of water for every 2 inches of fish. Anything more than this can cause overcrowding and then death.

Overfeeding

Overfeeding is another reason why fish die in outdoor ponds. When you feed a fish too much, it greatly increases the amount of waste they produce. This is particularly dangerous in small ponds, as it contaminates the water and removes important nutrients. 

Fertilizer

Lastly, the fish in your pond might be dying because of fertilizer pollution. This is common in properties where there are crops and a lot of farmland. The fertilizer introduces harmful chemicals to the water. It can also cause an overgrowth of algae. This is very dangerous because it prevents sunlight from reaching the pond. Fertilizer contamination is usually the cause when a lot of your pond fish die at once. A common sign of fertilizer poisoning in a pond is when the pond develops a thick green layer of algae on top.