Signs Of An Unhealthy Pond

Ponds are a great way to spend your time. Knowing the signs of an unhealthy pond is very important so you can jump to action if something is not right.

A pond’s appearance is not everything. You also need to promote a healthy environment, so that all plants and animals can flourish, and look amazing all year.

Here are some signs of an unhealthy pond:


Algae and weed growth

We should all agree that excessive algae or weed growth is terrible. One of the first things you will notice if your pond is becoming unhealthy is algae growth. 

Algae grows best when there is a rich supply of nitrogen, phosphorus, or nutrients in the water. Nitrogen is the byproduct of fish waste and decaying debris. 

If the water in a pond is not being either filtered properly or the pond has poor circulation, levels of nitrogen, nutrients, and phosphorus can spike. 

Since these are all catalysts for algae growth, they are a good indication if the levels are too high. 

Most people find that after a rainstorm the levels of phosphorus and nitrogen have increased. This is because of runoff bringing dirt and debris into the pond.

Rain in unavoidable, so try to keep an eye out on the levels of your pond after a rainstorm. 

If you are still in the works of building a pond I recommend trying to increase the height of the pond edges or diverting runoff paths away from the pond. 

This will ensure no dirt or other debris gets washed into the pond.

High nutrients comes from two main problems in a pond. 

The most common if the Over Feeding of the fish in a pond. 

If you notice fish food is being left at the bottom of your pond it means you are overfeeding.

The excess food will begin to break down and release all the nutrients it had into the water. 

The plants you have in the pond will not be able to filter out all the excess nutrients from the pond.

Another issue from overfeeding is high ammonia levels. If there’s too much ammonia in a pond it causes the fish to become sick and if not treated, it can lead to death.

The other reason for high nutrients is the lack of plants.

If a pond only has two or three plants it makes it very easy for nutrients levels to be more than the plants can handle.

Plants use the nutrients from the water to grow, but they use it in small amounts.

 So, adding in more plants will ensure that they are properly filtering the water and taking out the nutrients from fish waste or excess food.

If you notice high levels in your pond I recommend using Pond Cleanse to reduce the high levels. 

Phosphorus can take a long time to be naturally removed from a body of water and can easily become a problem during the rainy season. 

High nitrogen, phosphorus and nutrient levels can eventually to the illness of your fish. If these levels are too high it can cause suffocation for the fish.

Just like humans, fish need to breathe oxygen, and if nitrogen, phosphorus, and nutrients start to become high enough it limits the amount of oxygen available for fish.


Murky water

When you first set up your pond and add fish, you’ll notice that your pond is very clear and natural-looking. 

Although, over time, your pond water can turn very murky. This is usually caused by sediment or algae. 

As all of this debris builds up in the pond through falling leaves, fish waste, decaying plants, and algae the water quality and water clarity will worsen tremendously.

Water clarity is affected by sediment and algae because the particles associated with this issue are so small that they are unable to be filtered. 

I like to use API Pond Algae Cure, this clumps all the unfilterable particles together to then be filtered.

Keeping your pond water clear creates a natural healthy environment for your fish, but also adds to the pristine appearance.

Something I recommend doing is to get a glass jar and fill it full of your murky pond water and let it sit for 24 hours.

If the water becomes clear in 24 hours you have something in your pond preventing debris from settling. 

If the water remains cloudy, there is a pre-existing condition.

Also, ponds are more likely to appear murkier in the warmer summer months.


Yellow coloring in green plants

Signs Of An Unhealthy Pond

Yellowing of your plants is much more common than you think. 

I am not talking about one or two leaves turning yellow from dying off, but a whole plant or multiple plants turning yellow.

There are 4 main reasons for this occurrence: 

    • Fertilizer
      When fertilizing your plants, fertilize very carefully. Too much or too little can cause them to yellow. 


  • Insects/bugs
    Insects love to grub up on plants, they will eat and wear away all your plants. Mites and Aphids are the most common, you can easily wash them off in the water. This will lead to a tasty treat for your fish.


    • Too much sun
      Unfortunately, there is no plant sunscreen on the market. A sunburned plant can sometimes yellow, although when a plant gets too much sun the color usually turns brown. 


  • Submerged plant leaves
    Underwater leaves can cause a plant to yellow or brown. It’s fine if the stems are underwater, but if the leaf itself is, you will likely encounter some problems.



Bad odor

If you go out to your pond and smell a bad odor, everyone should know there is something wrong. 

Odor can come from a few things, but most commonly, broken down leaves and sticks called sludge, too much algae, or dead fish you may not have seen.

The best way to determine what the odor is coming from is by the smell.


Extensive amounts of algae will be easiest to identify, it has a bad earthly smell almost like compost. If you have a large amount of algae growth, that is most likely the problem.

The smell of algae is the easiest to get rid of, just remove the algae. 

This can be done by using a pond rake, adding Algae Eating Fish, reducing available nutrients, increase circulation and aeration, or using algae remover.


Broken down debris or sludge will smell closer to manure. Sludge forms from the decomposing sticks and leaves that may have been missed by a filter or skimmer.

After a piece of debris hits the bottom, whether that be a stick or some leaves, it starts to break down. 

The debris will release chemicals into the water and you will just be left with the debris matter. That is the sludge and it will give off a bad odor.

If you have ever completely drained your pond you will find this in small nooks and you will be surprised by the strength of the smell it gives off.


Dead fish

Signs Of An Unhealthy PondIf you’ve had a pond, most likely you’ve had at least one fish die. There can be several reasons for this to happen.

The most common cause of fish death is oxygen depletion. 

This is due because there are pollutants in your pond like ammonia or nitrite, which heavily interferes with a fish’s breathing through its gills.

You will know this is happening when your fish start to gasp at the surface.

Another cause for your fish to die is because of disease. Signs of an unhealthy pond fish disease include; little to no eating, odd swim patterns, and spots. 

By keeping your pond clean, aerated correctly, as well as stocked correctly will significantly reduce the chance of your fish to get a disease.